WO2021157345A1 - Water pressure fluctuation measuring system and water pressure fluctuation measuring method - Google Patents

Abstract

This water pressure fluctuation measuring system detects fluctuations in water pressure. A cable includes an optical fiber (F1) and is disposed on the surface of or in the sea floor so that the optical fiber (F1) expands and contracts in conjunction with fluctuations in water pressure. A light output unit (1A) outputs monitoring light to the optical fiber (F1). A partial reflection part (R11) is disposed on the path of the optical fiber (F1) in the cable, and partially reflects the monitoring light. A light reception unit (1B) receives the reflected light reflected by the partial reflection part (R11). A calculation unit (1C): measures the length of the optical fiber (F1) to the partial reflection part (R11) on the basis of the round-trip propagation time of the received reflected light; and monitors the changes over time of such length.

Description

Water pressure fluctuation measurement system and water pressure fluctuation measurement method

The present invention relates to a water pressure fluctuation measuring system and a water pressure fluctuation measuring method.

Various methods for measuring the movement of the ground are known. For example, there is known a technique called a wire sensor in which a wire that conducts an electric signal is laid on the ground, and a broken wire is detected as an abnormality to monitor a landslide. Further, there is known a technique called an optical wire sensor in which the conductive wire is replaced with an optical fiber cable to perform the same monitoring.

In the optical wire sensor, a method of detecting that the optical fiber is broken and the propagation of light is obstructed, or an optical fiber cable is laid so that the bending loss increases according to the tension applied to the optical fiber cable, and the loss changes. (Patent Documents 1 to 3). For example, in Patent Document 3, a mechanism for automatically feeding / winding the cable according to the expansion and contraction of the ground is provided at the end point of the optical fiber cable, and a minute loss is given to the optical fiber at each monitoring point. The loss giving point is fixed to the ground, and when the optical fiber cable moves with respect to the ground, the loss giving point moves. This loss addition point is detected by OTDR (Optical Time Domain Reflectometry), which will be described later.

Further, there is known a technique of an optical passive element called FBG (Fiber Bragg Grating), which provides an optical fiber with a diffraction grating that selectively reflects a specific wavelength by irradiation with ultraviolet rays or the like. This FBG can also be provided at various points in the optical fiber cable in the same manner as the loss imparting point described above. For example, if the FBG is housed in a package in which the period of the diffraction grating changes due to an external influence (for example, distortion or temperature), the reflection wavelength of the FBG changes according to the environment of the installation location. By irradiating the FBG with probe light and measuring the reflected light, it is possible to obtain information on the distortion and temperature of the place where the FBG is provided. In a configuration in which a plurality of FBGs are provided on one optical fiber cable, for example, by arranging and designing the initial reflection wavelengths of the FBGs so as not to overlap each other, each FBG can be distinguished by the wavelength of the reflected light.

As a method for checking the health of an optical fiber transmission line, a technique called OTDR is known in which pulsed light is incident on an optical fiber and the power of the reflected and returned light is measured together with the time until the light returns. .. Since weak reflected light is generated in the optical fiber due to Rayleigh scattering, it is observed as a locus that the reflected light is weakened under the influence of the transmission loss as the pulsed light propagates in the optical fiber. At this time, if the optical fiber has a reflection point, a bending loss, or the like, the power of the reflected light rises or falls at a specific place on the locus, so that the place can be identified. As described above, in the OTDR, the place where the power fluctuation occurs can be distinguished by measuring the time until the reflected light returns (Patent Document 4).

A method of applying an OTDR to a configuration in which a plurality of sensor elements are connected to the tip of one optical fiber is also generally used. For example, in an optical wire sensor, when a plurality of sensor elements whose installation location conditions are reflected in bending loss are provided, the loss generated at each installation location should be monitored separately for each location by observing the OTDR trajectory. Can be done. Further, a technique of using an FBG as a reflecting element in an OTDR is also used. The OTDR used for such multipoint sensing is sometimes referred to as an interrogator.

In addition, a technique (Patent Documents 6 and 7) for monitoring the soundness of an optical amplification repeater by inserting a component that causes partial reflection in the middle of an optical fiber transmission line is known. A technique for identifying a location in combination with an OTDR is also disclosed. Further, there are also known techniques for detecting crustal movements combining GPS and acoustic ranging (Patent Document 8 and Non-Patent Document 1), and installing an optical transmitter / receiver for propagating light for ranging into water on the bottom of the water. (Patent Document 9).

Furthermore, there are several known methods for measuring changes in water pressure on the seafloor offshore in order to detect offshore tide levels and tsunami conditions. A typical method is to install a water pressure sensor on the seabed and transmit the measurement data to the land through a submarine cable (Non-Patent Document 2). Furthermore, a technique for detecting on land how the submarine cable itself changes under the influence of water pressure is also disclosed (Patent Document 10).

Japanese Unexamined Patent Publication No. 8-14952 Japanese Patent No. 4187866 Japanese Patent No. 36535550 Special Table 2007-518365 Japanese Patent No. 3440721 Japanese Patent No. 3509748 Japanese Patent No. 3391341 U.S. Pat. No. 3,860,900 Japanese Patent No. 2906232 Japanese Patent No. 2586838

However, the above technology assumes the detection of sudden changes in the ground such as landslides and slope failures, and reflects minute and slow movements of the ground such as crustal movements in changes in the length of optical fibers. It cannot be detected by letting it.

Strain sensors, such as FBG strain sensors, are used to monitor local strain, such as monitoring strain in buildings such as bridges and structures such as aircraft, while observing long baseline lengths. , It is not suitable for the application of integrating and detecting the expansion and contraction of the ground in a large range such as crustal movement.

The above-mentioned OTDR is generally used for measuring the entire length of an optical fiber cable, and it is not possible to monitor the expansion and contraction of the cable in the middle.

In addition, the above-mentioned method for detecting the offshore tide level and tsunami condition detects the effect of changes in water pressure on the submarine cable with a long optical interferometer, and detects changes in water pressure for each section of the submarine cable. In order to know, it was necessary to configure a large number of long optical interferometers, which required many core wires, which was economically difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to detect fluctuations in water pressure.

The water pressure fluctuation measuring system according to one aspect of the present invention includes a first optical fiber, and a cable provided on the ground or in the ground of the sea floor so that the first optical fiber expands and contracts according to the fluctuation of water pressure. An optical output unit that outputs monitoring light to the first optical fiber, a partial reflection unit that is provided on the path of the first optical fiber in the cable and partially reflects the monitoring light, and the portion. Based on the reciprocating propagation time of the light receiving unit that receives the reflected light reflected by the reflecting unit and the received reflected light, the length of the first optical fiber to the partial reflecting unit is measured, and the length thereof is connected. It has a calculation unit that monitors time changes.

In the water pressure fluctuation measuring method according to one aspect of the present invention, a cable including a first optical fiber having a partial reflection portion that partially reflects the monitoring light is provided on the path, and the first optical fiber is water pressure. It is provided on the ground or in the ground of the sea floor so as to expand and contract with fluctuations, the monitoring light is output to the first optical fiber, the reflected light reflected by the partial reflection portion is received, and the received reflected light is received. The length of the first optical fiber up to the partial reflection portion is measured based on the reciprocating propagation time of the above, and the change over time is monitored.

According to the present invention, fluctuations in water pressure can be detected.

It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 1. FIG. It is a figure which shows typically the structural example of the partial reflection part. It is a figure which shows an example of the acquired OTDR waveform. It is the figure which magnified the rise of the peak corresponding to the partial reflection part on the 1st and 2nd measurement days. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 2. It is a figure which shows the OTDR waveform on the 1st measurement day which concerns on Embodiment 2. FIG. It is a figure which magnified the rise of the peak on the 1st and 2nd measurement days at the point 1 where a partial reflection part was installed and the point 2 where a partial reflection part was installed. It is a figure which shows the example of the fiber length from the point 0 to the point 4 observed on the 1st and 2nd measurement days by the surveying system which concerns on Embodiment 2. FIG. It is a figure which shows the example of the OTDR waveform when the reflectance of a partial reflection part is the same. It is a figure which shows the example of the OTDR waveform when the reflectance of a partial reflection part is increased as the distance from the OTDR apparatus increases. It is a figure which shows typically the structure of the surveying system 700 which introduced the error suppression technique. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 3. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 4. It is a figure which shows the OTDR waveform obtained by the surveying system which concerns on Embodiment 4. FIG. It is a figure which shows the example of the laying path of this surveying system when the optical fiber cable cannot branch. It is a figure which shows the example of the laying path of this surveying system when an optical fiber cable can be branched. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 5. It is a figure which shows typically the structure of the modification of the surveying system which concerns on Embodiment 5. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 6. It is a figure which shows the monitoring result of the optical fiber by the surveying system which concerns on Embodiment 6. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 7. It is a figure which shows typically the structure of the OADM branch node. It is a figure which shows typically the structure of the modification of the surveying system which concerns on Embodiment 7. It is a figure which shows typically the structure of the modification of the surveying system which concerns on Embodiment 7. It is a figure which shows the example which configured the route redundant network between each OADM branch node and two land stations in Embodiment 8. It is a figure which shows typically the configuration of the OADM branch node corresponding to the route redundant network configuration. It is a figure which shows typically the mode of the sensor cable (branch line cable) which branches from the trunk cable which concerns on Embodiment 9. FIG. It is a figure which shows typically the configuration example of the surveying system which concerns on Embodiment 10. It is a figure which shows typically the structure of the surveying system which concerns on Embodiment 11. It is explanatory drawing of the mechanism that the submarine cable feels the water pressure fluctuation. It is a figure which shows an example of the result of the water pressure measurement which concerns on Embodiment 12.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

Embodiment 1
The surveying system 100 according to the first embodiment will be described. The surveying system 100 is configured to detect the movement of the ground by applying an OTDR (Optical Time Domain Reflectometry) to an optical fiber laid on the ground. FIG. 1 schematically shows the configuration of the surveying system 100 according to the first embodiment. The surveying system 100 includes an OTDR device 1, an optical fiber cable F1, and a partial reflection unit R11.

The optical fiber cable F1 is laid so that an appropriate tension acts so as to cross the seabed in a range where the movement of the ground 110 is to be monitored, for example. In the optical fiber cable F1, a partial reflection portion R11 is inserted at a point where the movement of the ground 110 in the observation area is monitored. One end of the optical fiber cable F1 is connected to an OTDR device 1 installed in a land station or the like. In this example, the partial reflection unit R11 is configured as a partial reflection unit that reflects a part of the incident light.

Here, an example of the configuration of the partial reflection portion R11 will be described with reference to FIG. This is a configuration widely used as a method for realizing a partial reflection portion. In the partially reflecting portion R11, the light L is incident from the left direction in the figure, and a part of the light L is reflected to become the reflected light RL and returns to the left direction. Further, the passing light PL, which is the majority of the light L not reflected by the partial reflecting portion R11, passes through the partial reflecting portion R11 and exits to the right.

The incident light L is demultiplexed by the optical coupler 2 into the passing light PL and the light that is the source of the reflected light. The light that is the source of the reflected light passes through the light attenuation element 3, reaches the total reflection element 4 at the end, is totally reflected, and is combined by the optical coupler 2 through the original path, and becomes the reflected light RL. Is transmitted toward the light source side. As the total reflection element 4, a ferrule or the like in which gold is vapor-deposited on the end face can be used.

The reflectance and transmittance in this configuration are first roughly determined by the branching ratio of the optical coupler 2. For example, if the branch ratio of the optical coupler is 80:20, the transmittance is attenuated by 80%, that is, about 1 dB, and the reflected light RL is attenuated by at least 4%, that is, about 14 dB because it passes through the optical coupler twice. As will be described later, since it is assumed that a plurality of partial reflection portions are provided on the optical fiber cable, the balance between transmission and reflection is ensured by appropriately selecting the branch ratio of the optical coupler. Next, by adjusting the amount of attenuation of the light attenuation element 3, it can be adjusted in the direction of lowering the reflectance. Since the optical attenuation element 3 can be realized by fusion-bonding (splicing) the optical fibers with each other by slightly shifting the central axes of the two optical fibers, individual adjustment is easy. With these adjustment parameters, the reflectance of each partial reflection portion can be made different. In this configuration, since it acts as a partial reflection portion in only one direction, it is not necessary to consider the influence of multiple reflections. In addition to this, various forms such as an FBG having a low reflectance and a module configuration using a 2-core ferrule are known as the partial reflecting portion, and are applicable.

The OTDR device 1 can execute an OTDR that outputs pulsed light, which is monitoring light, to the optical fiber F1 (first optical fiber), monitors the return light due to Rayleigh scattering, and acquires the trajectory of the reflected light power. It is configured as a device. The OTDR device 1 includes an optical output unit 1A, an optical reception unit 1B, and a calculation unit 1C. The optical output unit 1A outputs pulsed light to the optical fiber F1. The optical receiver 1B converts the return light from the optical fiber F1 into an electric signal. The calculation unit 1C monitors the electric signal output from the light reception unit 1B, calculates and processes the locus drawn by the power of the return light, detects the position of the partial reflection unit on the fiber, and records it. Hereinafter, the trajectory drawn by the power of the return light is referred to as an OTDR waveform.

In other words, the calculation unit 1C can be understood as measuring the length of the optical fiber F1 up to the partial reflection unit R11 based on the reciprocating propagation time of the return light (reflected light) and monitoring the change over time. ..

Note that the monitoring of the change in the length of the optical fiber F1 described as being performed by the arithmetic unit 1C may be performed by a control unit or the like provided by an external device provided outside the OTDR device 1. That is, the calculation unit 1C measures the length of the optical fiber F1 up to the partial reflection unit R11 based on the reciprocating propagation time of the return light (reflected light), and according to the measurement result of the measured length of the optical fiber F1. , A control unit of an external device or the like may monitor the change over time.

The detection of the movement of the ground 110 of the surveying system 100 will be described. The OTDR device 1 performs OTDR measurement on the optical fiber F1, automatically detects the partial reflection points contained therein, and positions the partial reflection points on the optical fiber, that is, the fiber from the OTDR to each partial reflection point. Record the length. FIG. 3 shows an example of the acquired OTDR waveform. The vertical axis is the power of the return light (for example, logarithmic representation), and the horizontal axis is the fiber length. Since the light pulse is strongly reflected by the partial reflection portion R11 at the point corresponding to the position where the partial reflection portion R11 is provided, the power of the return light is locally increased and the peak P1 ₁₁ is generated. The calculation unit 1C automatically detects and outputs the peak.

By repeatedly measuring the above OTDR measurements at intervals, the relatively slow movement of the ground 110 is detected. Hereinafter, the measurement date will be referred to as a first measurement date and a second measurement date.

When the optical fiber cable F1 expands and contracts as a result of movement on the ground 110, the positions of the partial reflection portions on the first measurement day and the second measurement day appear to move. FIG. 4 shows an enlarged view of the rise of the peak corresponding to the partial reflection portion R11 on the first and second measurement days. The waveform on the first measurement day is shown by a broken line, and the waveform on the second measurement day is shown by a solid line. As can be seen in FIG. 4, the peak P2 ₁₁ on the second measurement day is slightly shifted to the left of _{the peak P1 11} on the first measurement day. This indicates that the optical fiber cable F1 is slightly shrunk and the cable length is shortened, and the partial reflection unit R11 is slightly closer to the land station (that is, the OTDR device 1).

As described above, according to this configuration, the movement of the ground at the position where the partial reflection portion is provided can be detected by comparing the peak positions due to the reflected light from the same partial reflection portion on two separated measurement days. ..

The optical fiber cable F1 has sufficient friction with the seabed and is laid so that an appropriate tension remains, so that the optical fiber cable F1 expands and contracts in the same manner according to the expansion and contraction of the seabed, that is, the ground 110. In order to lay the optical fiber cable F1 so that an appropriate tension remains, it is also possible to lay it while checking the residual tension by, for example, measuring the strain of the optical fiber F1 by BOTDR (Brillouin OTDR) on board. Is.

Embodiment 2
The surveying system 200 according to the second embodiment will be described. FIG. 5 schematically shows the configuration of the surveying system 200 according to the second embodiment. The surveying system 200 is provided with a plurality of partial reflection portions as compared with the surveying system 100. Specifically, the surveying system 200 has a configuration in which three partial reflection units R12 to R14 are added beyond the partial reflection unit R11. The installation location of the OTDR device 1 is referred to as point 0. Although the optical fiber cable F1 is installed on the ground as in FIG. 1, the ground is not shown.

The detection of the movement of the ground of the surveying system 200 will be described. The surveying system 200 acquires OTDR waveforms on the first and second measurement dates, similarly to the surveying system 100 according to the embodiment. FIG. 6 shows an OTDR waveform on the first measurement day according to the second embodiment. In FIG. 6, since the four partial reflection portions R11 to R14 are arranged in order from the side closest to the OTDR device 1, the four peaks P1 ₁₁ , P1 ₁₂ , and P1 at the four points 1 to 4 corresponding to these are arranged in order. ₁₃ and P1 ₁₄ appear in that order.

In the present embodiment, the measurement results on the first and second measurement dates are compared as in the first embodiment. FIG. 7 shows an enlarged view of the rise of peaks on the first and second measurement days at the point 1 where the partial reflection portion R11 is installed and the point 2 where the partial reflection portion R12 is installed. The waveform on the first measurement day is shown by a broken line, and the waveform on the second measurement day is shown by a solid line.

Comparing the changes in point 1 and point 2, the peak shift amount at point 2 is larger than the peak shift amount at point 1. Therefore, it can be seen that the cable length is shortened in both the OTDR device 1 (point 0) and the point 1 and the point 1 and the point 2. This is because if only the space between the OTDR device 1 and the point 1 contracts and there is no expansion or contraction beyond that point, the shift amount beyond the point 1 is the same as that between the OTDR device 1 and the point 1.

FIG. 8 shows an example of measuring the cable length from point 0 to point 4 observed by the surveying system 200 on the first and second measurement days. In this example, the interval between the first and second measurement dates is about one year. In the cable length measurement value of FIG. 8, the influence of temperature and tide has already been removed. The fiber length between points 1 and 2 is referred to as L12, and the fiber length between points 2 and 3 is referred to as L23.

As shown in FIG. 8, during the period from the first measurement date to the second measurement date, the points 0 to 1 are about 2.3 cm, the points 1 to 2 are about 3.2 cm, and the points 2 to 3 are about 1. It is 0.0 cm, and points 3 to 4 are shrunk by about 0.3 cm. By providing a plurality of partial reflection portions in this way, it is possible to observe the movement of the ground with a resolution in units of the section sandwiched between the two partial reflection portions.

Generally, as light propagates through the optical fiber F1, the power decreases due to transmission loss. Therefore, if the reflectance of each partial reflection portion is the same, the peak appearing in the OTDR waveform becomes lower as the reflection point is farther from the OTDR device 1. In general, the power of the return light in the OTDR is relatively weak, so that the peak due to the reflected light tends to be buried in the noise level.

Therefore, in this configuration, the partial reflector in the place near the OTDR device 1 where the cumulative loss is small has a low reflectance, and the partial reflector in the place far from the OTDR device 1 where the cumulative loss is large has a high reflectance. Is desirable. That is, assuming that the reflectances of the partially reflecting portions R11 to R14 are Rf1 to Rf4, it is preferable that Rf1 <Rf2 <Rf3 <Rf4. FIG. 9 shows an example of an OTDR waveform when the reflectances of the partial reflection portions R11 to R14 are the same, and FIG. 10 shows an example of an OTDR waveform when the reflectance of the partial reflection portion is increased as the distance from the OTDR device 1 increases. show. In FIG. 9, the peaks P1 ₁₃ and P1 _{14 of the} partial reflection portions R13 and R14 are buried in the noise level NL, but in FIG. 10, the peaks in a distant place are not buried in the noise level NL and are easy to recognize. ..

This makes it possible to reduce the average number of OTDR waveforms, that is, the measurement time. By shortening the measurement, the influence of environmental factors such as temperature changes during that period can be naturally reduced.

Here, the error suppression technology in this surveying system will be explained. FIG. 11 schematically shows the configuration of the surveying system 700 into which the technology for suppressing these errors has been introduced. The surveying system 700 includes a DTS (Distributed Temperature Sensor) device 701, a data processing device 702, a polarization scrambler 703, a high-precision clock supply unit 704, a wavelength division multiplexing separator WC0, and an optical fiber in the surveying system 100 in the land station 710. It has a configuration in which F70 is added.

It is known that the optical fiber cable expands and contracts due to the external environment, especially the temperature change. Therefore, when trying to detect the movement of the ground using this surveying system in an environment where there is a temperature change, it is necessary to eliminate the influence of expansion and contraction of the optical fiber cable due to the temperature change. Therefore, in the present embodiment, the temperature of each location of the optical fiber cable is measured by DTS (Distributed Temperature Sensor).

As described above, the DTS device 701 distributes the temperature in the longitudinal direction of the optical fiber cable F1 and outputs the data as the DTS output data DAT2. The OTDR device 1 outputs the position of each reflection point on the cable as the OTDR output data DAT1 as described in the above-described embodiment. The data processing device 702 removes the influence of expansion and contraction of the optical fiber cable due to the temperature change based on the OTDR output data DAT1 and the DTS output data DAT2. The data processing device 702 can control the OTDR device 1 by the control signal CON1 and can control the DTS device 701 by the control signal CON2. In this embodiment, the measurement light of the DTS device 701 and the measurement light of this surveying system are measured on the same optical fiber by using the wavelength division multiplexing technology (WDM coupler WC10), but the light has no wavelength selectivity. It may be demultiplexed by a coupler and the measurement timings of the OTDR device 1 and the DTS device 701 may be controlled so as not to overlap each other for measurement, or another core wire (optical fiber) in the same cable 720 may be used. Since the temperatures are considered to be almost the same, the same effect can be obtained.

Next, the polarization scrambler 703 will be described. An optical fiber has a phenomenon called polarization mode dispersion in which a slight difference in propagation speed occurs depending on the polarization state of propagating light. Therefore, in this configuration, the polarization scrambler 703 is inserted into the output of the OTDR device 1 to constantly and randomly change the polarization state of the pulsed light. As a result, when the OTDR waveform is measured a plurality of times and the averaging process is performed, the influence of the polarization mode dispersion is also averaged, so that the fluctuation of the measured value depending on the polarization state can be suppressed. Since some old optical fiber cables have a large polarization mode dispersion, they are particularly effective when the old optical cable is reused.

Next, the high-precision clock supply unit 704 will be described. In recent years, the high-precision clock supply unit 704 has been commercially available and used as a device that receives radio waves from a GNSS (Global Navigation Satellite System) satellite to generate and supply a high-precision clock. The clock CLK from the high-precision clock supply unit realized in this way is supplied to the OTDR device 1. In particular, since the moving speed of the ground by plate tectonics is slow, about several centimeters a year, the stability of the clock in the low frequency range greatly affects the measurement accuracy. On the other hand, in general OTDR applications, such long-term measurement stability is not required, so there is a high possibility that accuracy will be insufficient as it is. In order to realize this surveying system, it is important to ensure long-term measurement accuracy by supplying such a high-precision clock to the OTDR device. As will be described later, in the case of a configuration in which a plurality of OTDRs exist in the surveying system, only one high-precision clock supply unit is required, and the clocks may be distributed. As will be described later, even when the OTDR device is installed remotely on the optical cable, for example, on the seabed, a high-precision clock supply unit is placed at one land station and distributed from there, so that the GNSS satellite radio waves do not reach the seabed. It is possible to observe based on a high-precision clock.

As described above, according to this configuration, the measurement accuracy of the movement of the ground can be ensured by applying all or part of the DTS, the polarization scrambler, and the high-precision clock supply to the surveying system.

Embodiment 3
In the above operating principle of this surveying system, it is assumed that the optical fiber cable is in contact with the ground with sufficient friction. In fact, for example, since a submarine cable is in contact with the seabed for a long distance, the accumulation of friction in the longitudinal direction is enormous, and when a large amplitude elongation occurs locally due to a submarine landslide or the like, the cable In some cases, the slip friction resistance of the cable exceeds the tension limit and the cable is cut.

From this, it can be expected that the ground and the cable will expand and contract together due to the friction that the cable originally has with the ground, even if no special fixing means is provided. However, especially when you want to observe the state of expansion and contraction of the ground in detail, there is a possibility that the cable will slip locally and the detailed information of the expansion and contraction of the ground will be smoothed. Therefore, an additive to the cable may be provided to strengthen the gripping force on the seabed.

As a method, a protrusion having a shape that makes it easier to catch on rocks on the seabed may be provided on the surface of the cable coating. This protrusion may be formed integrally with a member that covers the cable during the manufacture of the cable. Alternatively, a means for firmly fixing the cable to the seabed may be provided in places of the cable. The latter will be described in the third embodiment.

The surveying system 300 according to the third embodiment will be described. FIG. 12 schematically shows the configuration of the surveying system 300 according to the third embodiment. The surveying system 300 has a configuration in which fixtures A1 to A4 are added to the surveying system 200.

The optical fiber cable F1 was originally integrated with the seabed due to friction caused by contact with the seabed, but in addition to that, the fixtures A1 to A4 are provided in places to grip the seabed 310 more strongly. For the fixtures A1 to A4, a member that can penetrate the ground such as a pile may be used on land, and if it is on the seabed, a fixture shaped to improve catching on rocks on the seabed is wrapped around the cable and laid. Alternatively, a device such as an anchor having an appropriate weight that causes frictional force by settling on the sand on the seabed may be wrapped around the cable. For fixing such a device and a cable, for example, by using a component generally called a preformed stopper, it is possible to attach the cable while laying it. When wrapping and storing a long cable of hundreds of kilometers, the fixture may get in the way or damage the cable, so it is desirable to install it while laying the cable.

The position and type of this fixture on the sensor cable may be changed as appropriate according to the condition of the seabed. There are no particular restrictions on the positional relationship between the partial reflector and the fixture. However, it is expected that by equipping the fixture close to the partial reflection part, the reliability of the contact of the partial reflection part with the ground will increase, which will help improve the reliability of the observation data.

Embodiment 4
In the first to third embodiments, only one optical fiber, that is, a configuration in which there is no branch in the middle is described, but in the subsequent embodiments, a surveying system in which the optical fiber is branched into a plurality of fibers will be described. FIG. 13 schematically shows the configuration of the surveying system 400 according to the fourth embodiment.

In the surveying system 400, the optical fiber cables F2 and F3 (second optical fiber) are branched from the optical fiber cable F1. In this example, the optical fiber F1 is provided with partial reflection portions R11 to R14, ... In order from the side of the OTDR device 1, similarly to the surveying systems 200 and 300.

An optical coupler C1 is provided between the partial reflection portion R11 and the partial reflection portion R12, and the optical fiber F2 is branched. The optical fiber F2 is provided with partial reflection portions R21 to R23, ... In order from the side of the optical coupler C1.

An optical coupler C2 is provided between the partial reflection portion R13 and the partial reflection portion R14, and the optical fiber F3 is branched. The optical fiber F3 is provided with partial reflection portions R31, R32, ... In order from the side of the optical coupler C2.

FIG. 14 shows an OTDR waveform obtained by the surveying system 400. For convenience of explanation, the waveforms from the optical fibers F1, F2, and F3 are drawn separately, but in reality, one waveform is observed by the total of these waveforms. As can be seen from FIG. 14, the peaks of the partial reflection portions can be identified as long as the fiber lengths from the OTDR device 1 to the partial reflection portions do not overlap. Assuming that the optical fiber length from the branch point is 50 km, even if one optical fiber cable is provided with about 10 partial reflection portions, the size of each reflection portion is several cm, so that the probability is high. It can be said that the reflection peaks rarely overlap. Even if the reflection peaks overlap, it can be solved by inserting a dummy optical fiber of several meters at the branch point. Check the degree of overlap of the reflection peaks in the temporary connection state before installation, and insert a dummy fiber or cut the root of the branch cable a little short before connecting to the branch.

Therefore, according to this configuration, it is possible to detect the movement of the ground on the path where the optical fiber cable is laid, as in the above-described embodiment.

Hereinafter, this branch configuration will be referred to as a passive branch (depending on the coupler). The utility of this branch configuration will be described. In short, compared to the one-stroke sensor cable arrangement without branching, the sensor cable arrangement with branching can limit the range affected by the cable failure at the branching destination. This is referred to as the first utility of the branch configuration.

The area where you want to place the sensor cable is a place where the movement of the ground is noticeable, and there is a relatively high risk that such a place will naturally cause momentary and large-amplitude displacement, landslide, collapse, etc., and the cable There is also a high risk of being damaged. Therefore, the branch configuration becomes effective. This is because the range of influence of cable failure can be limited.

The first utility of the branch configuration will be described with reference to FIGS. 15 and 16. Here, the partial reflection portion in the monitoring area MA is simply represented by a circle, and the branch portion is simply represented by a square mark. If the sensor cable is installed with a single stroke as shown in FIG. 15, no information beyond the location where the cable failure has occurred cannot be obtained. On the other hand, in the case of the branch configuration as shown in FIG. 16, the influence of the cable failure can be limited to the branch cable.

Embodiment 5
In this embodiment, a branch configuration using wavelength division multiplexing will be described. Hereinafter, this branch configuration will be referred to as passive branching (by WDM coupler).

FIG. 17 schematically shows a configuration example of the surveying system 500 according to the fifth embodiment. Since each of the optical fiber and the partial reflection portion of the surveying system 500 is the same as that of the surveying system 400, the description thereof will be omitted.

The surveying system 500 is provided with a plurality of OTDR devices 11 to 13, in which three OTDR devices 11 to 13 have different transmission wavelengths. The OTDR device 11 is also referred to as a first OTDR device, and the OTDR devices 12 and 13 are also referred to as a second OTDR device. Further, in the surveying system 500, the optical couplers C1 and C2 are replaced with WDM couplers WC1 and WC2, respectively.

The OTDR devices 11 to 13 are connected to the optical fiber F1 via the wavelength division multiplexing separator WC0, and output pulsed light having different wavelengths λ1 to λ3. Here, the wavelength λ1 is also referred to as a first wavelength, and the wavelengths λ2 and λ3 are also referred to as a second wavelength.

The WDM coupler WC1 selectively branches the pulsed light having a wavelength of λ2 and outputs it to the optical fiber F2, and returns the reflected return light from the optical fiber F2 to the optical fiber F1.

The WDM coupler WC2 selectively branches the pulsed light having a wavelength of λ3 and outputs it to the optical fiber F3, and the reflected return light from the optical fiber F3 returns to the optical fiber F1 by the WDM coupler WC2.

Therefore, the return light having wavelengths λ1 to λ3 returns to the wavelength division multiplexing separator WC0 via the optical fiber F1. In this example, the wavelength division multiplexing separator WC0 has bidirectionality, separates the return light for each wavelength, and outputs the return light of wavelengths λ1 to λ3 to the OTDR devices 11 to 13, respectively. As a result, each of the OTDR devices 11 to 13 can independently monitor the return light from the optical fibers F1 to F3.

In the present embodiment, the partial reflection portion may partially reflect wavelength-independently, and R11, R12, R13, ... Only in the vicinity of λ1 (first wavelength), R21, R22, R23, ... · May be a partial reflection portion having wavelength selectivity such that is only in the vicinity of λ2 (second wavelength), R31, R32, ... Is only in the vicinity of λ3. In the latter case, if the loss of wavelengths other than λ1 can be reduced, the observable range of λ2 and λ3 can be expanded, and the wavelength range other than λ1, λ2 and λ3 of the cable F1 can be used for other purposes such as communication. It will be easier.

The utility of this passive branch (by WDM coupler) will be explained. First, as with passive branching (depending on the coupler), there is a first utility of the branching configuration. That is, when a sensor cable failure occurs, the range affected by the failure can be limited.

Comparing the passive branching by the WDM coupler with the passive branching by the coupler, the optical coupler branching has the advantage that the number of OTDRs does not need to be increased, but has the disadvantage that the observable range is shortened due to the loss due to the branching. In addition, if the number of branches and the number of reflection points are large, the correspondence between the branch lines and the reflection points may be mistaken, resulting in erroneous observation. That is, although a branch configuration can be realized, the scale is somewhat limited.

On the other hand, passive branching by WDM coupler has the disadvantage that multiple OTDRs are required, but physically branched cables can be managed as if they were independent cables, and confusion errors are unlikely to occur. .. Moreover, since the loss at the branch portion can be reduced, it is possible to avoid a decrease in the observable range. That is, the configuration using the WDM coupler enables passive branching with a higher degree of freedom in design than the configuration using the coupler. Hereinafter, this will be referred to as the second utility of the branch configuration.

It is also possible to carry out embodiments 3 and 4 together. An example is shown in FIG. Since the contents are the same as those of the third and fourth embodiments, the description thereof will be omitted. In the example of FIG. 18, the order is optical coupler branching (branching by optical couplers C3 and C4) after the wavelength branching, but the present invention is not limited to this, and wavelength branching is also possible before the optical coupler branching.

Embodiment 6
In the embodiment described above, an optical amplifier cannot be inserted in the communication path. This is because, in general, an optical amplifier transmits light in only one direction, so that the reflected return light is blocked there, and OTDR measurement cannot be performed. If the optical amplifier cannot be applied, the range that can be surveyed is limited to a place close to the land, and the desired area cannot be observed.
Therefore, in the following, a means for enabling observation of an area away from the land by using an optical amplifier will be described. FIG. 19 schematically shows a configuration example of the surveying system 600 according to the sixth embodiment. The surveying system 600 is an example in which a surveying system is attached to a submarine optical cable system used for data transmission. The method of branching is passive branching (using a WDM coupler). That is, this embodiment is a description of a technique for applying an optical amplifier to the fifth embodiment.

As mentioned above, the optical amplifier may transmit in only one direction, and in the communication cable including the optical amplifier, the upstream and downstream optical fibers are treated as a pair.

In the submarine optical cable system, a fiber pair FP having an optical fiber FT (third optical fiber) for uplink and an optical fiber FR (fourth optical fiber) for downlink is provided. The communication device 611, which is not directly related to the surveying system, is connected to the optical fiber FT via the wavelength division multiplexing device 612, and is connected to the optical fiber FR via the wavelength separator 613. As the wavelength multiplexing device 612 and the wavelength separator 613, for example, AWG (Arrayed Waveguide Grating) and WSS (Wavelength Selective Switch) are generally used.

In this configuration, the OTDR device 1 that outputs the pulsed light of λ1 is also connected to the optical fiber FT via the wavelength multiplexing device 612 and connected to the optical fiber FR via the wavelength separator 613. As a result, the OTDR device 1 can output the pulsed light to the optical fiber FT and receive the return light from the optical fiber FR. The wavelength band for the OTDR device 1 and the wavelength band for the communication device 611 are assigned separately.

One or more optical amplification repeaters AU are inserted into the fiber pair FP in order to compensate for the loss of the transmitted optical signal. The optical amplification repeater AU is provided with an optical amplifier AT that amplifies the light transmitted through the optical fiber FT for uplink and an optical amplifier AR that amplifies the light transmitted through the optical fiber FR for downlink. Further, the optical amplification repeater AU is provided with a path P such as reflected light that branches the return light propagating in the reverse direction of the upstream optical fiber FT and couples it to the downstream optical fiber FR. In the path P, for example, an optical coupler is provided on the input side of the optical amplifier AT to branch the return light, and the optical coupler provided on the output side of the optical amplifier AR via the optical fiber transmits the return light to the optical fiber for downlink. Combine with FR. In the following, the optical amplification repeater AU, the path P, the optical fiber FT, and the optical fiber FR constitute an optical amplification relay system that amplifies and transmits light.

Further, a WDM coupler WC is provided at an arbitrary position of the optical fiber FT, but actually at the output of the optical amplifier in the form of being integrated with the optical amplification repeater AU, and the pulsed light having a wavelength of λ1 is branched to the ground. Output to the optical fiber F1 for mobile survey. Further, the return light from the optical fiber cable F1 is coupled to the optical fiber FT by the WDM coupler WC, and then coupled to the optical fiber FR via the path P in the optical amplification repeater AU. After that, the return light is branched by the wavelength separator 613 and returned to the OTDR device 1 for reception. As a result, the OTDR device 1 can survey the section from the land to the optical fiber F1.

FIG. 20 shows the monitoring result of the optical fiber F1 by the surveying system 600. As shown in FIG. 20, in the surveying system 600, since the transmission loss is periodically compensated by the optical amplification repeater AU, a periodic saw waveform appears. The peak of the reflected light by the partial reflection portions R11 to R14 is observed as a reflection peak before the WDM coupler WC. Thereby, as in the above-described embodiment, the movement of the ground can be detected by measuring the reflection peak positions on the first and second measurement days.

In this embodiment, the route from land to entering the optical fiber F1 is also included in the OTDR measurement, but it hardly contributes to the survey. It is possible to contribute to the survey by incorporating a partial reflection portion of λ1 in the middle of the path, but it is not preferable because there is a concern that it may affect the communication on the communication device 611 side sharing the cable.

Needless to say, it is possible to apply passive branching by a coupler after entering the branching cable of the optical fiber F1 shown in FIG.

In the embodiment of FIG. 19, the wavelength used for the OTDR survey was only λ1, but in the form of applying the optical amplifier in FIG. 18, a plurality of wavelengths are assigned to the surveying system, and the passive branching by the WDM coupler is further applied. Needless to say, it is also possible.

With the configuration as in this embodiment, an optical amplifier can be applied to this surveying system, and it is possible to survey a place away from the land.

Embodiment 7
In the sixth embodiment, the optical amplifier can be applied and the area far from the land can be observed, but as can be seen from FIG. 20, the section of less interest is also included in the OTDR measurement. , There is a drawback that there is a lot of waste in measurement. Therefore, in the seventh embodiment, by installing the OTDR device on the seabed, a realization means that enables an observation network closer to the area to be observed is provided. FIG. 21 schematically shows the configuration of the surveying system 601 according to the seventh embodiment. The surveying system 601 is a modification of the surveying system 600 according to the sixth embodiment.

The surveying system 601 is also an example of realization in which a surveying system is attached to the submarine optical cable system used for data transmission. The method of the OADM (Optical Add-Drop Multiplexer) node in the wavelength division multiplexing communication system is used to realize the branching. In the OADM branch node, components such as the OTDR installed in the land station of the surveying system described above are arranged. In other words, it has a configuration like an overhanging station installed on the seabed.

In this way, since it is necessary to receive power from the cable in order to install and drive an active device such as an OTDR on the seabed, this branch configuration is called an active branch. In such a configuration, the communication between the land and the active branching device is the same as the general wavelength path, and therefore the description of the realization method will be omitted.

An embodiment of FIG. 21 will be described. The components such as the submarine cable communication system (communication device 611, wavelength division multiplexing 612 and wavelength separator 613), optical amplification repeater AU and fiber pair FP are the same as those in FIG. 19, and the OTDR device 1, optical fiber cable F1 , The components such as the partial reflection units R11, R12, and R13 are the same as those in the above-described embodiment of the survey system, and thus the description thereof will be omitted.

Looking at the whole, the OADM branch node 618 is inserted in the middle of the submarine communication cable, and the sensor cable is branched from there. That is, the OADM branch node corresponds to a device called a BU (Branching Unit) in a submarine cable communication system.

What is common with BU is insulation and water pressure resistance. In order to enable OTDRs and communication devices to be installed on the seabed, it is necessary to design a power-saving design, enable heat dissipation through the pressure-resistant housing, and ensure reliable insulation between the feeder line potential and the ground potential. ..

The difference from BU is that it does not supply power to the cable at the branch destination. In a general BU, a very difficult technique for branching a feeder line is required, but in this surveying system, it is not necessary to supply power to the sensor cable, and there is no burden on it. Therefore, it is not necessary to install power supply switching related equipment that occupies most of the mountable space in the housing in a general BU, and that space can be used to accommodate the OADM branch node, and the optical amplifier repeater AU may also be accommodated integrally. There is also. It is also possible to mount seismic sensors such as acceleration sensors. If optical amplification relay is required at the branch destination, it is desirable to first branch and extend the cable at the communication BU, and then provide a branch BU with the sensor cable.

In FIG. 21, the feeding line in the cable and the power receiving and feeding functions in each device are not shown. Therefore, in FIG. 22, the part of the OADM branch node 618 is taken out and the power feeding relationship is also shown. The contents will be explained.

In the OADM branch node 618, a specific wavelength (λ1 in FIG. 19, a third wavelength) of the signal light transmitted by wavelength division multiplexing in the backbone cable 620 is added-dropped. The OADM branch node 618 includes optical couplers WC1 and WC2 that have wavelength selectivity for light of wavelength λ1. A communication control unit (communication device) 615 (also referred to as a second communication device) that controls the OADM branch node is connected via an optical transceiver. Here, Tx and Rx are abbreviations for Transmitter and Receiver, respectively. This Tx can be transmitted at the wavelength λ1. This communication control unit constantly communicates with 614, which is an opposite device on the land side, through a wavelength path of wavelength λ1. Specifically, the optical signal (first optical signal) having a wavelength of λ1 output from the communication device 614 propagates through the optical fiber FT and is demultiplexed from the optical fiber FT by the optical coupler WC1 (first optical coupler). It is received by Rx (first receiving unit). The optical signal (second optical signal) of wavelength λ1 output from Tx (first transmitter) is combined with the optical fiber FR by the optical coupler WC2 (second optical coupler), and is combined with the optical fiber FR by the communication device 614. Received. The OTDR device 1 surveys the sensor cable and passes the result to the communication control unit 615. The power feeding unit 616 receives power from the power feeding conductor SL and supplies power to the communication control unit 615, the OTDR device 1, and the like.

The communication device 614 (also referred to as the first communication device) has an important role of constantly transmitting the clock from the high-precision clock supply unit to the OTDR placed on the seabed in addition to various control signals. This is because radio waves from the GNSS (Global Navigation Satellite System) satellite, which is a high-precision clock source, cannot be received in the sea. The data measured by the OTDR device 1 on the seabed is transmitted to the land communication device 614 via the communication control unit 615.

Although the surveying system 601 has been described as including the surveying system 100 in the amplified relay optical transmission system, as shown in FIGS. 23 and 24, the surveying system 400 having a branched configuration is used instead of the surveying system 100. Alternatively, it may be configured to include a surveying system 501 having 500, or both. Here, the illustration of the surveying system including the surveying system 500 having a branched configuration is omitted. In the survey system 603, the OADM branch node 618 of the survey system 602 is replaced with the OADM branch node 619. The OADM branch node 619 has a configuration in which the OTDR device 1 of the OADM branch node 618 is replaced with the OTDR devices 11 to 13 and the wavelength multiplexing separator WC0 included in the survey system 500. Even in that case, only one communication device 615 and one transmission / reception unit may be used. A synchronization clock can be distributed to a plurality of OTDRs, survey data can be collected, and the data can be time-division-multiplexed into a signal having one wavelength λ1 and transmitted to the communication device 614.

Embodiment 8
In the remote observation network having a plurality of OADM branch nodes as described above, in order to increase the availability of the trunk cable against a failure, both ends of the trunk cable are connected to two land stations to form a route redundancy configuration. It is also possible. FIG. 25 shows a realization example. FIG. 25 is an example of a surveying system 630 in which the trunk cable 620 is provided with OADM branch nodes 631 to 634 corresponding to the OADM branch node 618A.

FIG. 26 shows a configuration example of the OADM branch node 618A. The OADM branch node 618A is a modification of the above-mentioned OADM branch node 618. As shown in FIG. 26, the OADM branch node 618A has two sets of optical transceivers in the communication control unit 615 so that it can communicate with the two land stations 621 and 622, and the OADM filter is extended.

The OADM branch node 618A has a configuration in which optical couplers WC3 and WC4 are added to the OADM branch node shown in FIG. In the OADM branch node 618A, the communication control unit 615 is provided with two Tx and two Rx. The communication control unit 615 constantly communicates with the communication devices provided in the land stations 621 and 622, which are opposite devices on the land side, through the wavelength path of the wavelength λ1. Here, the communication device 614 provided in the land station 621 is referred to as a first communication device, and the communication device 614 provided in the land station 622 is also referred to as a third communication device.

The optical signal (first optical signal) having a wavelength of λ1 output from the communication device (first communication device) of the land station 621 propagates through the optical fiber FT and is opticald by the optical coupler WC1 (first optical coupler). It is demultiplexed from the fiber FT and received by one Rx (first receiving unit). The optical signal (second optical signal) of wavelength λ1 output from one Tx (first transmitter) is combined with the optical fiber FR by the optical coupler WC2 (second optical coupler), and the land station 621 It is received by the communication device (third communication device) of.

The optical signal (third optical signal) of wavelength λ1 output from the communication device (third communication device) of the land station 622 propagates through the optical fiber FR and is opticald by the optical coupler WC3 (third optical coupler). It is demultiplexed from the fiber FR and received by the other Rx (second receiver). The optical signal (fourth optical signal) of wavelength λ1 output from the other Tx (fourth transmitter) is combined with the optical fiber FT by the optical coupler WC4 (fourth optical coupler), and the land station 622 It is received by the communication device (third communication device) of.

As a result, the OADM branch node 618A is constantly communicating with both the land station 621 (first observation station) and the land station 622 (second observation station).

The two land stations 621 and 622 receive survey data from each of the OADM branch nodes 631 to 634 in normal times, and transmit the data to the data center via the data communication network 640. For example, the survey data of the OADM branch node 631 reaches the land stations 621 and 622 and is transmitted to the data center, respectively. In this way, the same survey data arrives at the data center in duplicate, so in normal times it is judged that both are normal, and they are aggregated into one for recording and processing.

According to this configuration, for example, when a cable failure occurs at a location marked with a cross in FIG. 25, the data from the OADM branch nodes 631 to 633 goes through the land station 621, and the data from the OADM branch node 634 goes through the land station. It reaches the data center via 622. That is, duplication of the communication path between the OADM branch node and the land station is provided. Furthermore, by ensuring communication between the two land stations and between the data center, the data center detects that one of the data has been interrupted when the same data should have arrived, and the data continues to be delivered. Data can be adopted, recorded and processed. By such an operation, it can be made strong against a cable failure and has the effect of increasing availability.

Embodiment 9
The utility of the above-mentioned active branch configuration will be described. In short, the role of each cable can be clearly separated in the survey observation network. In the configuration that does not use the active branch, the optical cable also serves as the sensor cable and the communication cable, but the roles of both can be separated by the configuration of the active branch. This is referred to as the third utility of the branch configuration.

This will be described with reference to FIG. 27. In this survey observation network, there are roughly two types of optical fiber cables. One is applied to trunk cables, etc., and it is desirable to use the same type of cable as the communication cable from the economical point of view. This is called a trunk line specification cable type. The other is a sensor cable. This is called a sensor specification cable type.

On the other hand, the cable components of the observation network can be broadly classified into two types. One is the trunk cable 900, which consists of trunk line specification cable types. It is responsible for communication and power supply functions, and is installed avoiding areas with unstable terrain as much as possible. The optical fiber core wire in it is mainly for communication, and its use as a sensor is not the main purpose. From the economical point of view, it is desired to apply the same cable as the communication cable to the cable itself, its connecting parts, and the connecting method.

Another cable component is the branch cables 920 and 950. The branch cable consists of a trunk line specification cable type and a sensor specification cable type connected. The feed line is not included in the branch cable. Alternatively, even if the feeder line is included, it is completely insulated from the feeder line in the backbone cable 900 by making it unused or unconnected. By doing so, it becomes possible to positively install the sensor cable in an area where there is a high risk of the cable being damaged but the observation priority is high. This is because if a failure occurs in the cable to which the feeder is connected, the failure will spread to the entire observation network to which the feeder is connected.

Here, the sensor specification cable type sections 925, 945, and 955 in each branch cable are cables for detecting expansion and contraction of the ground, and include a plurality of partial reflection portions Rxx, and are covered so that sufficient friction with the seabed can be obtained. have. On the other hand, the trunk line specification cable type sections 921 and 951 in each branch cable are sections for connecting the trunk cable and the branch cable.

Cables 923 and 953 branched from OADM branch nodes 902 and 905 on the backbone cable 900 are also trunk line specification cable types, but do not include the feeder line, or even if they include the feeder line, they are unused or unconnected. Therefore, it is completely insulated from the power supply line in the trunk cable 900. This cable and sections (replacement repair work assumption area) 922 and 952 consisting of the trunk line specification cable type on the branch cable side are connected using the connection parts and connection method of the trunk line specification cable type.

There is a risk of damage to the sensor specification cable type part included in the branch cable, so it is necessary to prepare a repair method in advance. However, the sensor specification cable type itself should be laid with tension left, friction with the seabed is important, etc., and the performance as a sensor should be emphasized, and when the cable is damaged and it becomes impossible to survey. It is expected that it will be difficult to pull up the damaged part and repair it, and it is considered that a realistic recovery method is to lay a new branch cable and replace it. The technology, parts, and construction methods for pulling up the cable placed on the seabed to the ship and connecting it to the new cable have been established for the communication cable (main line specification cable type), but it should be newly prepared for the sensor specification cable type. Is uneconomical.

Considering such replacement work, provide a section of the trunk line specification cable type with a sufficient length on the OADM branch node side of the branch cable. In addition, take a route and lay it in a place that does not interfere with such construction. In this construction, an anchor with a blade is run to intentionally cut the vicinity of the obstacle point (Cutting Drive), and the cable at a point slightly away from the cutting point is hooked on the anchor and pulled up on board. Then, the damaged or water-running cable section is cut off, a spare cable for repair is inserted, reconnected, and returned to the seabed. A desirable work area for this work is a relatively flat and open area that does not interfere with such work. In FIG. 27, it is schematically shown as replacement repair work assumption areas 922 and 952 on the branch cable side.

FIG. 27 shows the state of the branch cable 950 after it has been replaced and repaired. In order to disconnect the sensor specification cable type section 945, which has become unable to perform sufficient measurement due to a failure, the cable between the sensor specification cable type section 945 and the cable 953 is cut by an anchor operation, and the cable of the new sensor specification cable type section 955 is cut. And the cable 953 are connected at the connection point 956, and the connection point 956 is gently lowered to the bottom of the sea.

In this work, the cut end of the cable 953 is once pulled up on the ship, but if the OADM branch node 905 is pulled and moves or is lifted at that time, there is a high possibility that a secondary failure will occur on the trunk cable 900 side. The cable 953 needs to be long enough to prevent this from happening. Specifically, it is desirable that the OADM branch node 905 and the replacement / repair work assumed area 952 be separated from each other by 3 to 5 times or more the water depth.

By adopting an active branch configuration, it becomes easier to realize such division of roles of cables, it becomes easier to protect the backbone cable, and at the same time, it becomes easier to cover the observation area where there is a risk of cable damage. This is a survey observation network design that maximizes the third utility of the branch configuration.

However, the device of this embodiment, that is, the device of properly using the sensor specification cable type and the trunk line specification cable type, is possible even with passive branching, although the effect is limited, and is not limited to active branching.

Needless to say, in this configuration, the first utility of the branch configuration, that is, the utility that the ripple range when a cable failure occurs can be suppressed in a limited manner as compared with the one-stroke writing.

Embodiment 10
Here, in the surveying system 200 according to the second embodiment, a case where the path for inputting the pulsed light is made redundant will be described. FIG. 28 schematically shows the configuration of the surveying system 201 in which the redundant configuration is applied to the surveying system 200 according to the second embodiment. In the surveying system 201, an OTDR device 10 (second OTDR device) provided at another land station is added to the surveying system 200. The OTDR 10 and the optical coupler C0 are connected by an optical fiber FA, and the optical fiber FA is coupled to the optical fiber F1 by the optical coupler C0. Here, the OTDR device 1 is also referred to as a first OTDR device.

According to this configuration, for example, when the optical fiber cable F1 fails at the location marked X in FIG. 28, the OTDR device 10 can be started up and the measurement of the return light can be continued. At this time, the distance from the OTDR device to each partial reflection portion apparently changes, but in reality, only L01 has changed, and the measurement beyond L12 has not changed and can be continued. In addition, although the redundant configuration composed of two routes has been described here, it is also possible to apply the redundant configuration by three or more routes.

Embodiment 11
In Non-Patent Document 1, the seabed is acoustically measured on board using a mirror transponder installed on the seabed, and the position of the ship is measured using a positioning satellite (Global Navigation Satellite System: GNSS). A technique for grasping fluctuations is disclosed. This method is called a GNSS-acoustic distance measurement coupling method or a GPS / A method. In this method, a mirror transponder that receives an acoustic signal from a ship and sends a response acoustic signal is fixedly installed on the seabed.

In this configuration, the absolute position of the fixture can be grasped by incorporating the mirror transponder function into a part or all of the fixture described in the third embodiment. FIG. 29 schematically shows the configuration of the surveying system 800 according to the eleventh embodiment. As shown in FIG. 29, mirror transponders TPD1, TPD2 and TPD4 are installed on the fixtures A1, A2 and A4, respectively.

By measuring the position of the mirror transponder with an acoustic signal from the ship 801 on the sea surface 820 that receives the radio wave from the GNSS satellite 802 like the survey system 800, the position of the mirror transponder can be detected by this configuration. Information can be given.

Further, in this configuration, the movement detection of the ground by the survey system 800 and the absolute survey by the GNSS-acoustic distance measurement coupling method can be used complementarily. Although the GNSS-acoustic distance measurement coupling method can grasp the absolute position, it is difficult to realize real-time performance and completeness. In addition, it is difficult to perform high-precision measurement in the deep sea, where the influence of fluctuations in the underwater sound velocity is large. On the other hand, according to the movement detection of the ground according to this configuration, it is difficult to measure the absolute amount of expansion and contraction of the ground, but since it is possible to monitor multiple points in real time regardless of the water depth, mutual complementation can be expected.

Note that the submarine cable including the optical fiber and the power supply line may be used as the driving power for the mirror transponder installed on the seabed. Power may be supplied from the power supply line included in the submarine cable, but since it is not desirable to include the power supply line in the optical fiber cable for sensing, optical energy is sent via the optical fiber (optical fiber power supply) to store electricity. , It is preferable to drive by this.

Embodiment 12
The configuration for measuring the expansion and contraction of the ground described above can also measure the change in water pressure with the same configuration. In the present embodiment, first, the water pressure change measurement in the surveying system 100 of FIG. 1 according to the first embodiment will be described.

In this embodiment, it is assumed that the optical fiber cable F1 and the partial reflector R11 are installed on the seabed. The optical fiber cable F1 has a pressure-resistant structure having sufficient strength to withstand water pressure, but as a result of being slightly compressed by water pressure, the length of the optical fiber cable F1 is slightly extended. In addition, the ground expands and contracts due to changes in water pressure on the seabed, and if there is sufficient friction between the seabed and the cable, the cable expands and contracts accordingly. FIG. 30 shows an image of the latter action.

As shown in FIG. 30, the seabed is elastically deformed by being pushed by water pressure, and the method of elastic deformation of the seabed changes according to the change in water pressure. Since the optical fiber cable F1 crawls or is embedded in the seabed, the deformation of the seabed causes expansion and contraction in the longitudinal direction of the optical fiber cable F1. In order for this mechanism to work, friction is required between the optical fiber cable F1 and the seabed. It goes without saying that even if the optical fiber cable F1 is placed on the seabed, it will have friction, but if it is buried, the contact area will increase and it will be easier to obtain friction.

Although the amount of expansion and contraction of the optical fiber cable F1 described here is extremely small, it can be seen based on the wavelength (typically about 1 μm) of the light used for the measurement, which propagates through the optical fiber in the optical fiber cable F1. Is a sufficiently detectable amount.

As a result of these, the length of the optical fiber cable F1 changes slightly when the water pressure changes. When the length of the optical fiber cable F1 from the OTDR device 1 to the partial reflector R11 is precisely measured using the OTDR device 1, the change in water pressure is detected as the change in the length of the optical fiber cable F1. In the present embodiment, as compared with the first embodiment, the factor that causes the optical fiber cable F1 to expand and contract is not the crustal movement but the water pressure change, and the detection method is the same. The description of the operation related to the detection of the length of F1 will be omitted.

FIG. 31 shows an example of the result of the water pressure measurement according to the twelfth embodiment. In this measurement, the length of the cable from the OTDR device 1 to the partial reflector R11 was about 38 km. The cable section of about 11 km from the landing point was buried at a depth of about 1 m. The measurement resolution of the OTDR used is 5 cm, and data having a resolution finer than 5 cm is obtained by measuring the OTDR many times and obtaining the moving average.

Shown on the upper side of the graph in FIG. 31 is the change in the cable length up to the partial reflector R11. Each small circle is a single measurement of the cable length up to the partial reflector R11, and their moving averages are shown by the thick curve MA. The average value of the continuous observation period of about 3 days was used as the reference value, and the amount of change from the reference value was used as the vertical axis.

Looking at the moving average curve MA, it can be seen that a change in cable length of more than 10 cm appears. In this measurement, the measured value fluctuation (drift) of the OTDR has not been sufficiently removed, and fluctuations other than the true cable length change are included. However, it can be seen that there is a considerable correlation between the tide level change ΔH at the cable vicinity point shown by the dotted line on the lower side of the graph in FIG. 31 and the cable length change shown by the curve on the upper side of the graph. The tide level graph shows the high tide level at the top and the low tide level at the bottom.

From this, it can be seen that the length of the submarine cable changes not only in a slow change of several centimeters a year due to crustal movements, but also in a relatively short time of several hours due to changes in water pressure such as tides. I understand.

By using a configuration in which a plurality of partial reflectors are connected in series on an optical fiber cable, that is, the surveying system 200 according to the second embodiment shown in FIG. 5, it is possible to measure the change in water pressure in units of installation sections of the partial reflectors. Is.

As mentioned above, the change in water pressure can be detected from the change in cable length, but in order to know the amount of change in water pressure, it is necessary to calibrate the coefficient at least for each cable section. This is because the coefficient by which the change in water pressure is converted into the change in cable length differs depending on the cable installation location depending on the method of fixing the cable to the seabed, the cable structure, the type of coating, and the like.

As such a calibration means, for example, a tidal phenomenon as shown in FIG. 31 can be used. Since the tide can be estimated for each sea area, it can be used to calibrate this coefficient. That is, for example, the water depth change ΔH0 at the high tide time and the low tide time in the sea area of a certain cable section can be calculated (may be actually measured), and the water pressure change ΔP can also be calculated from the water depth change ΔH0. On the other hand, from the above observation, it is possible to obtain the cable length change ΔL of the cable section between the high tide time and the low tide time. The ratio of these ΔL and ΔP is a coefficient. By performing such calibration work for each cable section in advance, when an abnormal wave such as a tsunami occurs, it is possible to obtain the height as a measured value with less error. For example, as shown in FIG. 5, when a plurality of partial reflection portions are provided on one cable, the coefficient may be calculated for each of the sections sandwiched between the two adjacent partial reflection portions.

Although the frequency of occurrence is low, the tsunami may be used for coefficient calibration. Since the tsunami height in each offshore sea area can be estimated from the tsunami height observed along the coast, the coefficient for each cable section can be calculated by comparing it with the change in cable length before and after the arrival of the tsunami in each cable section. Is obtained.

The tidal phenomenon and crustal movement can be separated by the difference in the speed of change in cable length. As mentioned above, the tidal phenomenon is about daily, and the crustal movement is expected to be an extremely slow drift-like change on a yearly basis. By performing data analysis in combination with crustal movement observation by surveying by a seafloor reference station as in Non-Patent Document 1, the reliability of measurement results can be further enhanced.

Since not only crustal movements but also tidal phenomena change relatively slowly, it is necessary to secure sufficient time margin such as performing OTDR measurements many times for averaging processing and performing measurement operations intermittently. can. However, if a tsunami is detected and used as an alarm information source, an algorithm that automatically detects the tsunami immediately is required at a sufficiently short measurement interval. Both slow-changing phenomena such as tides and crustal movements and fast-changing phenomena such as tsunamis can be integrated into a single measurement system. For phenomena that require immediate warning notification such as tsunami, it is also effective to prepare a separate detection algorithm according to the characteristics of changes in each phenomenon and provide a mechanism to automatically detect and notify as soon as possible. be.

Other Embodiments The present invention is not limited to the above embodiments, and can be appropriately modified without departing from the spirit. For example, in the above-described embodiment, the optical transmission line monitoring device has been described as being applied to a submarine optical network system, but this is merely an example. That is, it may be applied to any optical network system such as a land-based optical network system other than the submarine optical network system.

In the above-described embodiment, the OTDR using Rayleigh scattering has been described, but an OTDR using a non-linear scattering phenomenon such as Brilliant scattering or Raman scattering may be applied. Brilliant scattering and Raman scattering tend to have lower reflectance than Rayleigh scattering, and long-distance measurement is relatively difficult. Therefore, it is desirable to use OTDR by Rayleigh scattering.

Needless to say, the above-described embodiments can be combined as appropriate.

Further, if a desired reflectance can be achieved, another reflecting element such as an FBG other than the configuration shown in FIG. 2 may be used as the partial reflecting portion.

In the above-described embodiment, the number of partially reflecting portions provided on the optical fiber is merely an example, and an arbitrary number of partially reflecting portions may be provided on the optical fiber.

In the above-described embodiment, an example in which the optical fiber cable is laid on the ground of the seabed has been described, but if the place is filled with water, the optical fiber cable is laid on the ground of the bottom even outside the sea. Then, the movement of the ground and the fluctuation of the water pressure may be detected. For example, an optical fiber cable may be laid on the ground at the bottom of a lake or river other than the sea to detect movement of the ground or fluctuation of water pressure.

In the twelfth embodiment, it has been explained that the optical fiber cable can be buried not only on the seabed but also in the ground below the seabed, but this is not limited to the twelfth embodiment. That is, it goes without saying that in the above-described embodiment including the twelfth embodiment, the optical fiber cable may be laid on the seabed or buried in the ground below the seabed.

Part or all of the above embodiments may be described as in the following appendix, but are not limited to the following.

(Appendix 1) A cable provided on or in the ground on the sea floor so that the first optical fiber expands and contracts with fluctuations in water pressure, including the first optical fiber, and the first optical fiber are monitored. An optical output unit that outputs light, a partial reflection unit that is provided on the path of the first optical fiber in the cable and partially reflects the monitoring light, and a reflected light that is reflected by the partial reflection unit. An optical receiving unit to receive, a calculation unit that measures the length of the first optical fiber to the partial reflecting unit based on the reciprocating propagation time of the received reflected light, and monitors the change over time. A water pressure fluctuation measurement system.

(Appendix 2) The amount of change in water pressure is obtained by multiplying the amount of change in the length of the first optical fiber by a coefficient, and the coefficient is the high tide in the sea area where the first optical fiber is installed. The water pressure according to Appendix 1, which is obtained by dividing the amount of change in water pressure between time and low tide by the amount of change in the length of the first optical fiber between high tide and low tide. Fluctuation measurement system.

(Appendix 3) The optical output unit outputs the monitoring light at a first measurement timing and a second measurement timing after the first measurement timing, and the calculation unit outputs the monitoring light at the first measurement timing. Based on the difference between the length of the first optical fiber up to the partial reflection portion measured at the measurement timing of the above and the length of the first optical fiber up to the partial reflection portion measured at the second measurement timing. , The water pressure fluctuation measuring system according to Appendix 2, which monitors the fluctuation amount of the water pressure.

(Appendix 4) A plurality of the partial reflection portions are provided at different positions of the first optical fiber, and the calculation unit is a length of the first optical fiber between two of the plurality of partial reflection portions. The water pressure fluctuation measuring system according to Appendix 2 or 3, which monitors the fluctuation of the water pressure based on the fluctuation of the water pressure.

(Appendix 5) For each cable section divided by the plurality of partial reflection portions, the amount of change in water pressure between high tide and low tide and each cable section between high tide and low tide. The water pressure fluctuation measurement system according to Appendix 4, wherein the coefficient of each cable section is obtained from the amount of change in the cable length.

(Appendix 6) The water pressure according to Appendix 4 or 5, wherein the plurality of partial reflection portions are configured so that the larger the path light loss from the light output portion to the partial reflection portion, the higher the reflectance. Fluctuation measurement system.

(Supplementary note 7) The water pressure fluctuation measuring system according to any one of Supplementary note 4 to 6, wherein the cable is provided with a fixture for adding a gripping force to the ground or the ground.

(Appendix 8) The water pressure fluctuation measuring system according to Appendix 7, wherein the fixture is provided in the vicinity of a part or all of the plurality of partial reflection portions.

(Appendix 9) The water pressure fluctuation measurement according to Appendix 7 or 8, wherein a mirror transponder used for acoustic distance measurement in the sea is fixed to the fixture to output a response acoustic signal by receiving an acoustic signal. system.

(Appendix 10) A means for measuring the temperature of the first optical fiber in a distributed manner in the longitudinal direction is provided, and the length of the optical fiber due to the change over time of the temperature is determined from the amount of change in the length of the first optical fiber with time. The water pressure fluctuation measuring system according to any one of Supplementary note 1 to 9, which excludes the change in temperature.

(Appendix 11) The water pressure fluctuation measurement system according to Appendix 10, wherein the temperature measurement uses another optical fiber included in the same cable as the first optical fiber.

(Supplementary note 12) The description in any one of Supplementary note 1 to 11, further comprising a polarization scrambler that changes the polarization plane of the monitoring light in a pseudo-random manner before inputting the monitoring light into the first optical fiber. Water pressure fluctuation measurement system.

(Appendix 13) The water pressure fluctuation measuring system according to any one of Appendix 1 to 12, wherein the optical output unit, the optical receiving unit, and the arithmetic unit constitute an OTDR (Optical time domain reflectometer) device.

(Appendix 14) The water pressure fluctuation measuring system according to Appendix 13, wherein the OTDR device synchronizes an internal clock of the OTDR device with a clock signal supplied from the outside.

(Supplementary note 15) The water pressure fluctuation measurement system according to Supplementary note 14, wherein the clock signal supplied from the outside is generated based on a signal received from the satellite of the satellite positioning system.

(Appendix 16) A combined demultiplexing means and a second optical fiber branched from the first optical fiber by the combined demultiplexing means are provided and provided on the path of the second optical fiber. The water pressure fluctuation measurement system according to any one of Supplementary note 1 to 12, wherein a partial reflection unit that partially reflects the monitoring light is provided.

(Supplementary note 17) The water pressure fluctuation measuring system according to Supplementary note 16, wherein the combined demultiplexing means is an optical coupler having no wavelength selectivity.

(Appendix 18) A first OTDR device that outputs monitoring light of a first wavelength and a second OTDR device that outputs monitoring light of a second wavelength are provided, and the combined / demultiplexing means is a first. The water pressure fluctuation measuring system according to Appendix 17, wherein the optical coupler has wavelength selectivity to combine and demultiplex the wavelength of the above and the second wavelength.

(Appendix 19) An optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers whose forward directions are opposite to each other, and the optical amplification relay. An optical amplification relay system including a path that branches a part of light propagating in the third optical fiber in a direction opposite to the forward direction to reach the vessel and couples the light to the fourth optical fiber. An optical coupler provided on the path of the third optical fiber and having wavelength selectivity for light of the first wavelength, which couples the first optical fiber and the third optical fiber. The optical output unit outputs the monitoring light of the first wavelength in the forward direction of the third optical fiber, and the monitoring light of the first wavelength is transmitted from the third optical fiber by the optical coupler. The light reflected from the partial reflection portion provided in the first optical fiber is frequency-selectively branched into the first optical fiber, and is coupled to the third optical fiber by the optical coupler to obtain the above. It propagates in a direction opposite to the forward direction of the third optical fiber, is coupled to the fourth optical fiber by the path, propagates in the forward direction of the fourth optical fiber, and the optical receiver is said. The water pressure fluctuation measuring system according to any one of Supplementary note 1 to 15, wherein the reflected light from the partial reflecting portion provided in the first optical fiber is received via a fourth optical fiber.

(Appendix 20) The third and fourth optical fibers having opposite forward directions, an optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers, and the optical amplification relay. An optical amplification relay system including a path that branches a part of light propagating in the third optical fiber in a direction opposite to the forward direction to reach the vessel and couples the light to the fourth optical fiber. , A first optical signal having a third wavelength is transmitted in the forward direction of the third optical fiber and propagates in the forward direction of the fourth optical fiber, and a second optical signal having the third wavelength is transmitted. A first communication device connected to one end of the third and fourth optical fibers, a first receiving unit connected to the OTDR device and receiving the first optical signal, and the above. A second communication device having a first transmission unit for transmitting the second optical signal including the result obtained by the OTDR device, and the third optical fiber provided on the path of the third optical fiber. The path of the first optical coupler and the fourth optical fiber that selectively branch the first optical signal propagating in the forward direction of the optical fiber to the first receiving portion of the second communication device. The wavelength of the second optical signal provided above and output by the first transmitter of the second communication device so that the second optical signal propagates in the forward direction of the fourth optical fiber. The water pressure fluctuation measuring system according to any one of Appendix 13 to 15, further comprising a second optical coupler selectively coupled to the fourth optical fiber.

(Appendix 21) The first optical signal includes a clock signal generated by the first communication device based on a signal received from a satellite of a satellite positioning system and a command for controlling the OTDR device, and includes the OTDR. The water pressure fluctuation measuring system according to Appendix 20, wherein the device synchronizes the internal clock of the OTDR device with the clock signal included in the first optical signal.

(Appendix 22) A third optical signal having the third wavelength, which transmits the third optical signal having the third wavelength in the forward direction of the fourth optical fiber and propagates in the forward direction of the third optical fiber. A third communication device connected to the other end of the third and fourth optical fibers for receiving the optical signal of 4, and the fourth optical fiber provided on the path of the fourth optical fiber. A third optical coupler that selectively branches the third optical signal propagating in the forward direction to the second receiving portion of the second communication device, and provided on the path of the third optical fiber. The fourth optical signal output by the second transmitter of the second communication device is wavelength-selectively propagated so that the fourth optical signal propagates in the forward direction of the third optical fiber. In the second communication device including a second optical coupler coupled to the third optical fiber, the second receiving unit receives the third optical signal and the second transmitting unit receives the third optical signal. 20 is the water pressure fluctuation measuring system according to Appendix 20, which transmits the fourth optical signal including the result obtained by the OTDR apparatus.

(Appendix 23) The second communication device, the first to fourth optical couplers, and the OTDR device form an OADM (Optical add-drop multiplexer) branch node, and include the third and fourth optical fibers. A second optical fiber cable includes the third communication device from the first observation station provided with the first communication device via the observation area in which the first optical fiber is laid. The second communication device is connected to the observation station, communicates with the first observation station by the first and second optical signals, and communicates with the first observation station by the third and fourth optical signals. The water pressure fluctuation measuring system according to Appendix 22, which communicates with an observation station.

(Appendix 24) The cable includes a sensor cable for measuring fluctuations in water pressure and a trunk cable for communication and power supply, and the first optical fiber is included in the sensor cable. The hydraulic pressure fluctuation measuring system according to Appendix 19 or 20, wherein the sensor cable does not include a feeder, or the feeder conductor included is insulated from the feeder of the trunk cable.

(Appendix 25) The cable comprises a backbone cable for the purpose of communication and power supply, and a branch cable branched from the backbone cable by an OADM branch node for measuring fluctuations in water pressure, and the branch cable is the backbone. A cable branched from the cable and a sensor cable for measuring fluctuations in water pressure are connected and configured, and the first optical fiber is included in the sensor cable and branched from the trunk cable. The water pressure fluctuation measuring system according to Appendix 19 or 20, wherein the cable does not include a feeding wire conductor, or the feeding wire conductor included is insulated from the feeding line of the backbone cable.

(Appendix 26) Of the branch cables, a section consisting of a cable branched from the backbone cable is connected to the other end of the first portion whose one end is connected to the OADM branch node and one end to the sensor cable. 25. The water pressure fluctuation measuring system according to Appendix 25, wherein the other end of the second portion is connected to the other end of the second portion at the time of laying.

(Appendix 27) The length of the first portion is the length of the first portion and the first portion so that tension is not transmitted to the OADM branch node when the first portion and the second portion are connected. The water pressure fluctuation measuring system according to Appendix 26, wherein the connection point with the portion 2 and the OADM branch node are separated from each other by a length.

(Appendix 28) The first portion and the second portion are characterized in that they are installed in a place where cable replacement work including cable cutting and reconnection by anchor operation from a cable construction ship is performed. The water pressure fluctuation measuring system according to Appendix 26 or 27.

(Appendix 29) A plurality of the OTDR devices are installed at a plurality of points on the first optical fiber via an optical combine demultiplexing means, and the water pressure fluctuates using one of the plurality of OTDR devices. If a failure occurs in the optical fiber cable that connects the one OTDR device and the optical duplexing means corresponding to the one OTDR device by performing measurement and using another OTDR device as a spare, the spare OTDR device The water pressure fluctuation measurement system according to any one of Appendix 13 to 15, wherein the water pressure fluctuation measurement is continued using any one of the above.

(Appendix 30) A cable including a first optical fiber having a partial reflection portion that partially reflects the monitoring light is provided on the path of the seabed so that the first optical fiber expands and contracts as the water pressure fluctuates. Provided on the ground or in the ground, the monitoring light is output to the first optical fiber, the reflected light reflected by the partial reflection unit is received, and the reciprocating propagation time of the received reflected light is used as the basis. A method for measuring water pressure fluctuation, which measures the length of the first optical fiber up to a partial reflection portion and monitors the change over time.

(Appendix 31) The amount of change in water pressure is obtained by multiplying the amount of change in the length of the first optical fiber by a coefficient, and the coefficient is the high tide in the sea area where the first optical fiber is installed. The water pressure according to Appendix 30, which is obtained by dividing the amount of change in water pressure between time and low tide by the amount of change in the length of the first optical fiber between high tide and low tide. Fluctuation measurement method.

(Appendix 32) The monitoring light is output at the first measurement timing and the second measurement timing after the first measurement timing, and up to the partial reflection portion measured at the first measurement timing. The fluctuation amount of the water pressure is monitored based on the difference between the length of the first optical fiber and the length of the first optical fiber up to the partial reflection portion measured at the second measurement timing. 31. The method for measuring water pressure fluctuation.

(Appendix 33) A plurality of the partial reflection portions are provided at different positions of the first optical fiber, and are based on a variation in the length of the first optical fiber between two of the plurality of partial reflection portions. The water pressure fluctuation measuring method according to Appendix 31 or 32, which monitors the fluctuation of the water pressure.

(Appendix 34) For each cable section divided by the plurality of partial reflection portions, the amount of change in water pressure between high tide and low tide and each cable section between high tide and low tide. The water pressure fluctuation measuring method according to Appendix 33, wherein the coefficient of each cable section is obtained from the amount of change in the cable length.

(Supplementary note 35) The plurality of partial reflection portions are configured so that the larger the path light loss from the output source of the monitoring light to the partial reflection portion, the higher the reflectance. Water pressure fluctuation measurement method.

(Supplementary note 36) The method for measuring water pressure fluctuation according to any one of Supplementary note 33 to 35, wherein the cable is provided with a fixture for adding a gripping force to the ground or the ground.

(Appendix 37) The method for measuring water pressure fluctuation according to Appendix 36, wherein the fixture is provided in the vicinity of a part or all of the plurality of partial reflection portions.

(Appendix 38) The water pressure fluctuation measurement according to Appendix 36 or 37, wherein a mirror transponder used for acoustic distance measurement in the sea is fixed to the fixture to output a response acoustic signal by receiving an acoustic signal. Method.

(Appendix 39) The temperature of the first optical fiber is measured in a distributed manner in the longitudinal direction, and the change in the length of the optical fiber due to the change in the temperature with time is based on the amount of change in the length of the first optical fiber with time. The method for measuring water pressure fluctuation according to any one of Supplementary Provisions 30 to 38, which excludes the above.

(Supplementary note 40) The water pressure fluctuation measuring method according to Supplementary note 39, wherein the temperature measurement uses another optical fiber included in the same cable as the first optical fiber.

(Supplementary note 41) The method for measuring water pressure fluctuation according to any one of Supplementary note 30 to 40, wherein the plane of polarization of the monitoring light is changed pseudo-randomly before the monitoring light is input to the first optical fiber.

(Appendix 42) The length of the first optical fiber up to the optical output unit that outputs the monitoring light, the optical reception unit that receives the reflected light, and the partial reflection unit is measured, and the change over time is monitored. The method for measuring water pressure fluctuation according to any one of Supplementary note 30 to 41, wherein the calculation unit constitutes an OTDR (Optical time domain reflector) device.

(Supplementary note 43) The water pressure fluctuation measuring method according to Supplementary note 42, wherein the OTDR device synchronizes an internal clock of the OTDR device with a clock signal supplied from the outside.

(Supplementary note 44) The method for measuring water pressure fluctuation according to Supplementary note 43, wherein the clock signal supplied from the outside is generated based on a signal received from a satellite of a satellite positioning system.

(Appendix 45) The second optical fiber is branched from the first optical fiber by the combined demultiplexing means, and a partial reflection portion that partially reflects the monitoring light is provided on the path of the second optical fiber. The method for measuring water pressure fluctuation according to any one of Supplementary Provisions 30 to 41, which is provided.

(Supplementary note 46) The method for measuring water pressure fluctuation according to Supplementary note 45, wherein the combined demultiplexing means is an optical coupler having no wavelength selectivity.

(Appendix 47) The first OTDR device outputs the monitoring light of the first wavelength, the second OTDR device outputs the monitoring light of the second wavelength, and the combined / demultiplexing means is the first wavelength. The water pressure fluctuation measuring method according to Appendix 46, wherein the optical coupler has wavelength selectivity to combine and demultiplex the second wavelength.

(Appendix 48) The third and fourth optical fibers having opposite forward directions, an optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers, and the optical amplification relay. An optical amplification relay system including a path that branches a part of light propagating in the third optical fiber in a direction opposite to the forward direction to reach the vessel and couples the light to the fourth optical fiber. An optical coupler provided on the path of the third optical fiber, which couples the first optical fiber and the third optical fiber, and has wavelength selectivity for light of the first wavelength. The monitoring light of the first wavelength is output in the forward direction of the third optical fiber, and the monitoring light of the first wavelength is the first light from the third optical fiber by the optical coupler. The light reflected from the partial reflection portion provided in the first optical fiber and branched into the fiber in a wavelength-selective manner is coupled to the third optical fiber by the optical coupler, and the third optical fiber is coupled to the third optical fiber. Propagates in the direction opposite to the forward direction of the above, is coupled to the fourth optical fiber by the path, propagates in the forward direction of the fourth optical fiber, and propagates through the fourth optical fiber. The method for measuring water pressure fluctuation according to any one of Appendix 30 to 44, which receives the reflected light from the partial reflecting portion provided in the optical fiber of the above.

(Appendix 49) An optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers whose forward directions are opposite to each other, and the optical amplification relay. An optical amplification relay system including a path that branches a part of light propagating in the third optical fiber in a direction opposite to the forward direction to reach the vessel and couples the light to the fourth optical fiber. The second light having the third wavelength provided, transmitting the first optical signal having the third wavelength in the forward direction of the third optical fiber and propagating in the forward direction of the fourth optical fiber. A first communication device connected to one end of the third and fourth optical fibers for receiving a signal, a first receiving unit connected to the OTDR device and receiving the first optical signal, and a first receiving unit. A second communication device having a first transmission unit for transmitting the second optical signal including the result obtained by the OTDR device, and the third optical fiber provided on the path of the third optical fiber. A first optical coupler that selectively branches the first optical signal propagating in the forward direction of the third optical fiber to a first receiving portion of the second communication device, and the fourth optical fiber. The second optical signal provided on the path and output by the first transmission unit of the second communication device is propagated in the forward direction of the fourth optical fiber so that the second optical signal propagates in the forward direction of the fourth optical fiber. The method for measuring water pressure fluctuation according to any one of Appendix 42 to 44, wherein a second optical coupler that selectively couples to the fourth optical fiber is provided.

(Appendix 50) The first optical signal includes a clock signal generated by the first communication device based on a signal received from a satellite of a satellite positioning system and a command for controlling the OTDR device, and includes the OTDR. The method for measuring water pressure fluctuation according to Appendix 49, wherein the internal clock of the apparatus is synchronized with the clock signal included in the first optical signal.

(Appendix 51) A third optical signal having the third wavelength, which transmits the third optical signal having the third wavelength in the forward direction of the fourth optical fiber and propagates in the forward direction of the third optical fiber. A third communication device connected to the other end of the third and fourth optical fibers for receiving the optical signal of 4, and the fourth optical fiber provided on the path of the fourth optical fiber. A third optical coupler that selectively branches the third optical signal propagating in the forward direction to the second receiving portion of the second communication device, and provided on the path of the third optical fiber. The fourth optical signal output by the second transmitter of the second communication device is wavelength-selectively propagated so that the fourth optical signal propagates in the forward direction of the third optical fiber. A second optical coupler coupled to the third optical fiber is provided, and in the second communication device, the second receiving unit receives the third optical signal, and the second transmitting unit receives the third optical signal. 49. The method for measuring water pressure fluctuation according to Appendix 49, which transmits the fourth optical signal including the result obtained by the OTDR apparatus.

(Appendix 52) The second communication device, the first to fourth optical couplers, and the OTDR device form an OADM (Optical add-drop multiplexer) branch node, and include the third and fourth optical fibers. A second optical fiber cable includes the third communication device from the first observation station provided with the first communication device via the observation area in which the first optical fiber is laid. The second communication device is connected to the observation station, communicates with the first observation station by the first and second optical signals, and communicates with the first observation station by the third and fourth optical signals. The water pressure fluctuation measuring method according to Appendix 51, which communicates with an observation station.

(Appendix 53) The cable includes a sensor cable for measuring fluctuations in water pressure and a trunk cable for communication and power supply, and the first optical fiber is included in the sensor cable. The water pressure fluctuation measuring method according to Appendix 47 or 48, wherein the sensor cable does not include a feeder line conductor, or the feeder line conductor included is insulated from the feeder line of the trunk cable.

(Appendix 54) The cable comprises a backbone cable for the purpose of communication and power supply, and a branch cable branched from the backbone cable by an OADM branch node for measuring fluctuations in water pressure, and the branch cable is the backbone. A cable branched from the cable and a sensor cable for measuring fluctuations in water pressure are connected and configured, and the first optical fiber is included in the sensor cable and branched from the trunk cable. The method for measuring water pressure fluctuation according to Appendix 47 or 48, wherein the cable does not include a power supply line conductor, or the power supply line conductor included is insulated from the power supply line of the backbone cable.

(Appendix 55) Of the branch cables, a section consisting of a cable branched from the backbone cable is connected to the other end of a first portion whose one end is connected to the OADM branch node and one end to the sensor cable. The water pressure fluctuation measuring method according to Appendix 54, wherein the other end of the second portion is connected to the other end of the second portion at the time of laying.

(Appendix 56) The length of the first portion is the length of the first portion and the first portion so that tension is not transmitted to the OADM branch node when the first portion and the second portion are connected. The water pressure fluctuation measuring method according to Appendix 55, wherein the connection point with the portion 2 and the OADM branch node are separated from each other by a length.

(Appendix 57) The first portion and the second portion are characterized in that they are installed in a place where cable replacement work including cable cutting and reconnection by anchor operation from a cable construction ship is performed. The method for measuring water pressure fluctuation according to Appendix 55 or 56.

(Appendix 58) A plurality of the OTDR devices are installed at a plurality of points on the first optical fiber via an optical combine demultiplexing means, and the water pressure fluctuates using one of the plurality of OTDR devices. If a failure occurs in the optical fiber cable that connects the one OTDR device and the optical duplexing means corresponding to the one OTDR device by performing measurement and using another OTDR device as a spare, the spare OTDR device The method for measuring water pressure fluctuation according to any one of Appendix 42 to 44, wherein the water pressure fluctuation measurement is continued using any one of the above.

Although the invention of the present application has been described above with reference to the embodiments, the invention of the present application is not limited to the above. Various changes that can be understood by those skilled in the art can be made within the scope of the invention in the configuration and details of the invention of the present application.

This application claims priority based on Japanese application Japanese Patent Application No. 2020-18851 filed on February 6, 2020, and incorporates all of its disclosures herein.

A1 to A4 Fixture AR, AT Optical Amplifier AU Optical Amplifier Repeater C0 to C4, C11, C12, C21, C22 Optical Coupler CLK Clock DAT1 OTDR Output Data DAT2 DTS Output Data F1 to F5 Optical Fiber Cable (Optical Fiber)
FA, FR, FT, F61 to F64 Optical fiber FP Fiber pair P Return path of reflected light from transmission line R11 to R14, R21 to R23, R31, R32, R41, R42, R51, R52, Rxx Partial reflector Rx reception Instrument Tx Transmitter TPD1, TPD2, TPD4 Mirror transponder SL Power supply conductor WC, WC1, WC2 WDM coupler WC0 Wavelength division multiplexing separator 1, 10 to 13 OTDR device 1A Optical output unit 1B Optical receiver 1C Calculation unit 2 Optical coupler 3 Optical attenuation Element 4 All-reflecting elements 100, 200, 201, 300, 400, 500, 501, 600 to 603, 630, 700, 800 Survey system 310 Submarine 611, 614 Communication device 612 Wavelength division multiplexing 613 Wavelength separator 615 Communication control unit 616 Power supply unit 618, 618A, 619, 631 to 634, 902, 905 OADM branch node 620 Core cable 621, 622, 710 Land station 640 Data communication network 701 DTS device 702 Data processing device 703 Polarization scrambler 704 High-precision clock supply Part 720 Cable 801 Ship 802 GNSS Satellite 820 Sea surface 900 Trunk cable 920, 950 Branch cable 921, 951 Trunk specification cable type Section 922, 952 Replacement repair work expected area 923, 953 Cable 925, 945, 955 Sensor specification Cable type Section 956 connection point

Claims (58)

1. A cable including a first optical fiber and provided on the ground or in the ground of the seabed so that the first optical fiber expands and contracts as the water pressure fluctuates.
   An optical output unit that outputs monitoring light to the first optical fiber,
   A partial reflection portion provided on the path of the first optical fiber in the cable and partially reflecting the monitoring light, and a partial reflection portion.
   A light receiving unit that receives the reflected light reflected by the partial reflecting unit, and
   A calculation unit that measures the length of the first optical fiber up to the partial reflection unit based on the reciprocating propagation time of the received reflected light and monitors the change over time is provided.
   Water pressure fluctuation measurement system.
2. The amount of change in water pressure is obtained by multiplying the amount of change in the length of the first optical fiber by a coefficient.
   The coefficient is the amount of change in water pressure between high tide and low tide in the sea area where the first optical fiber is installed, and the length of the first optical fiber between high tide and low tide. Obtained by dividing by the amount of change in the coefficient,
   The water pressure fluctuation measuring system according to claim 1.
3. The optical output unit outputs the monitoring light at the first measurement timing and the second measurement timing after the first measurement timing.
   The calculation unit includes the length of the first optical fiber up to the partial reflection unit measured at the first measurement timing and the first optical fiber up to the partial reflection unit measured at the second measurement timing. The fluctuation amount of the water pressure is monitored based on the difference from the length of the water pressure.
   The water pressure fluctuation measuring system according to claim 2.
4. A plurality of the partial reflection portions are provided at different positions of the first optical fiber.
   The calculation unit monitors the fluctuation of the water pressure based on the fluctuation of the length of the first optical fiber between two of the plurality of partial reflection portions.
   The water pressure fluctuation measuring system according to claim 2 or 3.
5. For each cable section separated by the plurality of partial reflection portions,
   The coefficient of each cable section is obtained from the amount of change in water pressure between high tide and low tide of each cable section and the amount of change in cable length of each cable section between high tide and low tide.
   The water pressure fluctuation measuring system according to claim 4.
6. The plurality of partial reflecting portions are configured so that the larger the path light loss from the light output portion to the partially reflecting portion, the higher the reflectance.
   The water pressure fluctuation measuring system according to claim 4 or 5.
7. The cable is provided with a fixture for adding a gripping force on the ground or in the ground.
   The water pressure fluctuation measuring system according to any one of claims 4 to 6.
8. The fixture is provided in the vicinity of a part or all of the plurality of partial reflection portions.
   The water pressure fluctuation measuring system according to claim 7.
9. A mirror transponder used for acoustic distance measurement in the sea, which outputs a response acoustic signal by receiving an acoustic signal, is fixed to the fixture.
   The water pressure fluctuation measuring system according to claim 7 or 8.
10. A means for measuring the temperature of the first optical fiber in a distributed manner in the longitudinal direction is provided.
    From the amount of change in the length of the first optical fiber with time, the change in the length of the optical fiber due to the change in temperature with time is excluded.
    The water pressure fluctuation measuring system according to any one of claims 1 to 9.
11. The temperature measurement is characterized by using another optical fiber included in the same cable as the first optical fiber.
    The water pressure fluctuation measuring system according to claim 10.
12. A polarization scrambler that changes the polarization plane of the monitoring light in a pseudo-random manner before inputting the monitoring light into the first optical fiber is provided.
    The water pressure fluctuation measuring system according to any one of claims 1 to 11.
13. The optical output unit, the optical receiving unit, and the arithmetic unit constitute an OTDR (Optical time domain reflectometer) device.
    The water pressure fluctuation measuring system according to any one of claims 1 to 12.
14. The OTDR device is characterized in that the internal clock of the OTDR device is synchronized with a clock signal supplied from the outside.
    The water pressure fluctuation measuring system according to claim 13.
15. The clock signal supplied from the outside is generated based on a signal received from a satellite of a satellite positioning system.
    The water pressure fluctuation measuring system according to claim 14.
16. Combined demultiplexing means and
    A second optical fiber branched from the first optical fiber by the combined demultiplexing means is provided.
    A partial reflection portion provided on the path of the second optical fiber and partially reflecting the monitoring light is provided.
    The water pressure fluctuation measuring system according to any one of claims 1 to 12.
17. The combined demultiplexing means is an optical coupler having no wavelength selectivity.
    The water pressure fluctuation measuring system according to claim 16.
18. A first OTDR device that outputs monitoring light of the first wavelength,
    A second OTDR device that outputs monitoring light of a second wavelength is provided.
    The combined demultiplexing means is an optical coupler having wavelength selectivity for combining and demultiplexing a first wavelength and a second wavelength.
    The water pressure fluctuation measuring system according to claim 17.
19. With the third and fourth optical fibers whose forward directions are opposite to each other,
    An optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers.
    An optical beam having a path that reaches the optical amplifier repeater and branches a part of the light propagating in the third optical fiber in a direction opposite to the forward direction to be coupled to the fourth optical fiber. Amplification relay system and
    An optical coupler provided on the path of the third optical fiber and having wavelength selectivity for light of the first wavelength, which couples the first optical fiber and the third optical fiber, is provided.
    The optical output unit outputs the monitoring light of the first wavelength in the forward direction of the third optical fiber, and outputs the monitoring light of the first wavelength.
    The monitoring light of the first wavelength is wavelength-selectively branched from the third optical fiber to the first optical fiber by the optical coupler.
    The reflected light from the partial reflection portion provided in the first optical fiber is
    It is coupled to the third optical fiber by the optical coupler and propagates in a direction opposite to the forward direction of the third optical fiber.
    It is coupled to the fourth optical fiber by the path and propagates in the forward direction of the fourth optical fiber.
    The optical receiving unit receives the reflected light from the partial reflecting unit provided on the first optical fiber via the fourth optical fiber.
    The water pressure fluctuation measuring system according to any one of claims 1 to 15.
20. With the third and fourth optical fibers whose forward directions are opposite to each other,
    An optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers.
    An optical beam having a path that reaches the optical amplifier repeater and branches a part of the light propagating in the third optical fiber in a direction opposite to the forward direction to be coupled to the fourth optical fiber. Amplification relay system and
    A first optical signal having a third wavelength is transmitted in the forward direction of the third optical fiber, and a second optical signal having the third wavelength propagating in the forward direction of the fourth optical fiber is transmitted. A first communication device connected to one end of the third and fourth optical fibers to receive, and
    It has a first receiving unit that is connected to the OTDR device and receives the first optical signal, and a first transmitting unit that transmits the second optical signal including the result obtained by the OTDR device. , The second communication device,
    The first optical signal provided on the path of the third optical fiber and propagating in the forward direction of the third optical fiber is wavelength-selectively branched to the first receiving portion of the second communication device. The first optical coupler to do
    The second optical signal provided on the path of the fourth optical fiber and output by the first transmitting unit of the second communication device is the second optical signal of the fourth optical fiber. A second optical coupler that wavelength-selectively couples to the fourth optical fiber so as to propagate in the forward direction is provided.
    The water pressure fluctuation measuring system according to any one of claims 13 to 15.
21. The first optical signal includes a clock signal generated by the first communication device based on a signal received from a satellite of a satellite positioning system and a command for controlling the OTDR device.
    The OTDR device synchronizes the internal clock of the OTDR device with the clock signal included in the first optical signal.
    The water pressure fluctuation measuring system according to claim 20.
22. A fourth optical signal having the third wavelength that transmits the third optical signal having the third wavelength in the forward direction of the fourth optical fiber and propagates in the forward direction of the third optical fiber. A third communication device connected to the other end of the third and fourth optical fibers, which receives
    The third optical signal provided on the path of the fourth optical fiber and propagating in the forward direction of the fourth optical fiber is wavelength-selectively branched to the second receiving portion of the second communication device. With the third optical coupler
    The fourth optical signal provided on the path of the third optical fiber and output by the second transmission unit of the second communication device is the fourth optical signal of the third optical fiber. A second optical coupler that wavelength-selectively couples to the third optical fiber so as to propagate in the forward direction is provided.
    In the second communication device, the second receiving unit receives the third optical signal, and the second transmitting unit transmits the fourth optical signal including the result obtained by the OTDR device. ,
    The water pressure fluctuation measuring system according to claim 20.
23. The second communication device, the first to fourth optical couplers, and the OTDR device constitute an OADM (Optical add-drop multiplexer) branch node.
    An optical fiber cable including the third and fourth optical fibers is transmitted from a first observation station provided with the first communication device via an observation area in which the first optical fiber is laid. It is connected to the second observation station including the third communication device, and is connected to the second observation station.
    The second communication device communicates with the first observation station by the first and second optical signals, and communicates with the second observation station by the third and fourth optical signals.
    The water pressure fluctuation measuring system according to claim 22.
24. The cable consists of a sensor cable for measuring fluctuations in water pressure and a trunk cable for communication and power supply.
    The first optical fiber is included in the sensor cable.
    The sensor cable does not include a feeder, or the feeder conductor included is insulated from the feeder of the trunk cable.
    The water pressure fluctuation measuring system according to claim 19 or 20.
25. The cable consists of a backbone cable for communication and power supply, and a branch cable branched from the backbone cable by an OADM branch node for measuring fluctuations in water pressure.
    The branch cable is configured by connecting a cable branched from the backbone cable and a sensor cable for measuring fluctuations in water pressure.
    The first optical fiber is included in the sensor cable.
    The cable branched from the backbone cable does not include a feeder, or the feeder conductor included is insulated from the feeder of the backbone cable.
    The water pressure fluctuation measuring system according to claim 19 or 20.
26. Among the branch cables, the section consisting of the cable branched from the backbone cable has one end connected to the other end of the first portion connected to the OADM branch node and one end connected to the sensor cable. It is characterized in that it is configured by being connected to the other end of the portion at the time of laying.
    The water pressure fluctuation measuring system according to claim 25.
27. The length of the first portion includes the first portion and the second portion so that tension is not transmitted to the OADM branch node when the first portion and the second portion are connected. The length is such that the connection point of the OADM branch node and the OADM branch node are separated from each other.
    The water pressure fluctuation measuring system according to claim 26.
28. The first portion and the second portion are characterized in that they are installed in a place where cable replacement work including cable cutting and reconnection by anchor operation from a cable construction ship is performed.
    The water pressure fluctuation measuring system according to claim 26 or 27.
29. A plurality of the OTDR devices are installed at a plurality of points on the first optical fiber via photosynthetic demultiplexing means.
    Water pressure fluctuation measurement was performed using one of the plurality of OTDR devices, and the other OTDR device was used as a spare.
    If the optical fiber cable connecting the one OTDR device and the photosynthetic demultiplexing means corresponding to the one OTDR device fails, the water pressure fluctuation measurement is continued using one of the spare OTDR devices.
    The water pressure fluctuation measuring system according to any one of claims 13 to 15.
30. A cable containing a first optical fiber having a partial reflection portion that partially reflects the monitoring light is provided on the path, and the first optical fiber expands and contracts as the water pressure fluctuates on the ground or on the seabed. Provided inside
    The monitoring light is output to the first optical fiber, and the monitoring light is output.
    Receives the reflected light reflected by the partial reflection unit,
    Based on the reciprocating propagation time of the received reflected light, the length of the first optical fiber to the partial reflection portion is measured, and the change over time is monitored.
    Water pressure fluctuation measurement method.
31. The amount of change in water pressure is obtained by multiplying the amount of change in the length of the first optical fiber by a coefficient.
    The coefficient is the amount of change in water pressure between high tide and low tide in the sea area where the first optical fiber is installed, and the length of the first optical fiber between high tide and low tide. Obtained by dividing by the amount of change in the coefficient,
    The method for measuring water pressure fluctuation according to claim 30.
32. The monitoring light is output at the first measurement timing and the second measurement timing after the first measurement timing.
    The difference between the length of the first optical fiber up to the partial reflection portion measured at the first measurement timing and the length of the first optical fiber up to the partial reflection portion measured at the second measurement timing. To monitor the fluctuation amount of the water pressure based on
    The method for measuring water pressure fluctuation according to claim 31.
33. A plurality of the partial reflection portions are provided at different positions of the first optical fiber.
    The fluctuation of the water pressure is monitored based on the fluctuation of the length of the first optical fiber between two of the plurality of partial reflection portions.
    The method for measuring water pressure fluctuation according to claim 31 or 32.
34. For each cable section separated by the plurality of partial reflection portions,
    The coefficient of each cable section is obtained from the amount of change in water pressure between high tide and low tide of each cable section and the amount of change in cable length of each cable section between high tide and low tide.
    The method for measuring water pressure fluctuation according to claim 33.
35. The plurality of partial reflection portions are configured such that the larger the path light loss from the output source of the monitoring light to the partial reflection portion, the higher the reflectance.
    The method for measuring water pressure fluctuation according to claim 33 or 34.
36. The cable is provided with a fixture for adding a gripping force on the ground or in the ground.
    The method for measuring water pressure fluctuation according to any one of claims 33 to 35.
37. The fixture is provided in the vicinity of a part or all of the plurality of partial reflection portions.
    The method for measuring water pressure fluctuation according to claim 36.
38. A mirror transponder used for acoustic distance measurement in the sea, which outputs a response acoustic signal by receiving an acoustic signal, is fixed to the fixture.
    The method for measuring water pressure fluctuation according to claim 36 or 37.
39. The temperature of the first optical fiber was measured in a longitudinal direction and distributed.
    From the amount of change in the length of the first optical fiber with time, the change in the length of the optical fiber due to the change in temperature with time is excluded.
    The method for measuring water pressure fluctuation according to any one of claims 30 to 38.
40. The temperature measurement is characterized by using another optical fiber included in the same cable as the first optical fiber.
    The method for measuring water pressure fluctuation according to claim 39.
41. Before the monitoring light is input to the first optical fiber, the plane of polarization of the monitoring light is changed in a pseudo-random manner.
    The method for measuring water pressure fluctuation according to any one of claims 30 to 40.
42. An optical output unit that outputs the monitoring light, an optical reception unit that receives the reflected light, and a calculation unit that measures the length of the first optical fiber up to the partial reflection unit and monitors the change over time. Configure an OTDR (Optical time domain reflectometer) device,
    The method for measuring water pressure fluctuation according to any one of claims 30 to 41.
43. The OTDR device is characterized in that the internal clock of the OTDR device is synchronized with a clock signal supplied from the outside.
    The method for measuring water pressure fluctuation according to claim 42.
44. The clock signal supplied from the outside is generated based on a signal received from a satellite of a satellite positioning system.
    The method for measuring water pressure fluctuation according to claim 43.
45. The second optical fiber is branched from the first optical fiber by the demultiplexing means, and the second optical fiber is branched.
    A partial reflection portion that partially reflects the monitoring light is provided on the path of the second optical fiber.
    The method for measuring water pressure fluctuation according to any one of claims 30 to 41.
46. The combined demultiplexing means is an optical coupler having no wavelength selectivity.
    The method for measuring water pressure fluctuation according to claim 45.
47. The first OTDR device outputs the monitoring light of the first wavelength,
    The second OTDR device outputs the monitoring light of the second wavelength,
    The combined demultiplexing means is an optical coupler having wavelength selectivity for combining and demultiplexing a first wavelength and a second wavelength.
    The method for measuring water pressure fluctuation according to claim 46.
48. With the third and fourth optical fibers whose forward directions are opposite to each other,
    An optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers.
    An optical beam having a path that reaches the optical amplifier repeater and branches a part of the light propagating in the third optical fiber in a direction opposite to the forward direction to be coupled to the fourth optical fiber. Amplification relay system is provided
    An optical coupler provided on the path of the third optical fiber and having wavelength selectivity for light of the first wavelength, which couples the first optical fiber and the third optical fiber, is provided.
    The monitoring light of the first wavelength is output in the forward direction of the third optical fiber, and the monitoring light is output.
    The monitoring light of the first wavelength is wavelength-selectively branched from the third optical fiber to the first optical fiber by the optical coupler.
    The reflected light from the partial reflection portion provided in the first optical fiber is
    It is coupled to the third optical fiber by the optical coupler and propagates in a direction opposite to the forward direction of the third optical fiber.
    It is coupled to the fourth optical fiber by the path and propagates in the forward direction of the fourth optical fiber.
    The reflected light from the partial reflection portion provided in the first optical fiber is received via the fourth optical fiber.
    The method for measuring water pressure fluctuation according to any one of claims 30 to 44.
49. With the third and fourth optical fibers whose forward directions are opposite to each other,
    An optical amplification repeater that amplifies and relays light propagating through the third and fourth optical fibers.
    An optical beam having a path that reaches the optical amplifier repeater and branches a part of the light propagating in the third optical fiber in a direction opposite to the forward direction to be coupled to the fourth optical fiber. Amplification relay system is provided
    A first optical signal having a third wavelength is transmitted in the forward direction of the third optical fiber, and a second optical signal having the third wavelength propagating in the forward direction of the fourth optical fiber is transmitted. A first communication device connected to one end of the third and fourth optical fibers to receive, and
    It has a first receiving unit that is connected to the OTDR device and receives the first optical signal, and a first transmitting unit that transmits the second optical signal including the result obtained by the OTDR device. , The second communication device,
    The first optical signal provided on the path of the third optical fiber and propagating in the forward direction of the third optical fiber is wavelength-selectively branched to the first receiving portion of the second communication device. The first optical coupler to do
    The second optical signal provided on the path of the fourth optical fiber and output by the first transmitting unit of the second communication device is the second optical signal of the fourth optical fiber. A second optical coupler that wavelength-selectively couples to the fourth optical fiber so as to propagate in the forward direction is provided.
    The method for measuring water pressure fluctuation according to any one of claims 42 to 44.
50. The first optical signal includes a clock signal generated by the first communication device based on a signal received from a satellite of a satellite positioning system and a command for controlling the OTDR device.
    Synchronize the internal clock of the OTDR device with the clock signal included in the first optical signal.
    The method for measuring water pressure fluctuation according to claim 49.
51. A fourth optical signal having the third wavelength that transmits the third optical signal having the third wavelength in the forward direction of the fourth optical fiber and propagates in the forward direction of the third optical fiber. A third communication device connected to the other end of the third and fourth optical fibers, which receives
    The third optical signal provided on the path of the fourth optical fiber and propagating in the forward direction of the fourth optical fiber is wavelength-selectively branched to the second receiving portion of the second communication device. With the third optical coupler
    The fourth optical signal provided on the path of the third optical fiber and output by the second transmission unit of the second communication device is the fourth optical signal of the third optical fiber. A second optical coupler that is wavelength-selectively coupled to the third optical fiber so as to propagate in the forward direction is provided.
    In the second communication device, the second receiving unit receives the third optical signal, and the second transmitting unit transmits the fourth optical signal including the result obtained by the OTDR device. ,
    The method for measuring water pressure fluctuation according to claim 49.
52. The second communication device, the first to fourth optical couplers, and the OTDR device constitute an OADM (Optical add-drop multiplexer) branch node.
    An optical fiber cable including the third and fourth optical fibers is transmitted from a first observation station provided with the first communication device via an observation area in which the first optical fiber is laid. It is connected to the second observation station including the third communication device, and is connected to the second observation station.
    The second communication device communicates with the first observation station by the first and second optical signals, and communicates with the second observation station by the third and fourth optical signals.
    The method for measuring water pressure fluctuation according to claim 51.
53. The cable consists of a sensor cable for measuring fluctuations in water pressure and a trunk cable for communication and power supply.
    The first optical fiber is included in the sensor cable.
    The sensor cable does not include a feeder, or the feeder conductor included is insulated from the feeder of the trunk cable.
    The method for measuring water pressure fluctuation according to claim 47 or 48.
54. The cable consists of a backbone cable for communication and power supply, and a branch cable branched from the backbone cable by an OADM branch node for measuring fluctuations in water pressure.
    The branch cable is configured by connecting a cable branched from the backbone cable and a sensor cable for measuring fluctuations in water pressure.
    The first optical fiber is included in the sensor cable.
    The cable branched from the backbone cable does not include a feeder, or the feeder conductor included is insulated from the feeder of the backbone cable.
    The method for measuring water pressure fluctuation according to claim 47 or 48.
55. Among the branch cables, the section consisting of the cable branched from the backbone cable has one end connected to the other end of the first portion connected to the OADM branch node and one end connected to the sensor cable. It is characterized in that it is configured by being connected to the other end of the portion at the time of laying.
    The method for measuring water pressure fluctuation according to claim 54.
56. The length of the first portion includes the first portion and the second portion so that tension is not transmitted to the OADM branch node when the first portion and the second portion are connected. The length is such that the connection point of the OADM branch node and the OADM branch node are separated from each other.
    The method for measuring water pressure fluctuation according to claim 55.
57. The first portion and the second portion are characterized in that they are installed in a place where cable replacement work including cable cutting and reconnection by anchor operation from a cable construction ship is performed.
    The method for measuring water pressure fluctuation according to claim 55 or 56.
58. A plurality of the OTDR devices are installed at a plurality of points on the first optical fiber via photosynthetic demultiplexing means.
    Water pressure fluctuation measurement was performed using one of the plurality of OTDR devices, and the other OTDR device was used as a spare.
    If the optical fiber cable connecting the one OTDR device and the photosynthetic demultiplexing means corresponding to the one OTDR device fails, the water pressure fluctuation measurement is continued using one of the spare OTDR devices.
    The method for measuring water pressure fluctuation according to any one of claims 42 to 44.

Images